In anticipation of playing Octodad: Dadliest Catch with kiddo this weekend, I decided to look up some octopus-related facts to pepper throughout our gaming time, which we will hopefully be able to stream (new internet provider). In the earlier English-language reference works I own, the octopus is almost a mythical creature, one of those horrors that occupy the unknown depths of the ocean. The entry in the 1919 World Book (vol. 7, pp. 4340-4341), for example, makes me feel sorry for the poor, misunderstood octopus, as the World Book repeats over and over again that the octopus is a horrifying and scary creature:

OCTOPUS, ok' toh pus, a genus of deep-sea animals, of repulsive and frightful appearance. The soft, pear-shaped body of the animal is joined to the head by a short neck, and encircling the mouth are eight movable arms, on each of which there are two rows of powerful suckers. The arms are connected at the base by a web. It is these arms that give the creature its name, for octopus is derived from Greek words meaning having eight arms. The octopus cannot swim, but moves along the sea bottom by means of its arms. It lives in coral reefs and among rocks and is most common in the Mediterranean and Asiatic seas, although it reaches its greatest size on the Pacific coast — sometimes fourteen feet from tip to tip of extended arms. Generally the length of arm in the largest specimens is from three and one-half to four feet. The food of the octopus consists of crabs and other small shellfish.

Divers along coral banks are sometimes caught by the arms of these animals and death is caused by strangulation, drowning or fright. It is possible to loosen the grip of an octopus by seizing it on either side of the mouth and turning it inside out, but it is said that the hideous appearance of the animal is so terrifying that a victim is usually rendered helpless. The Chinese and Italians, who seek the octopus for food, catch the animal by running a pointed stick through the body.

For description of the class to which the octopus belongs see the article Cephalopoda.

The 11th edition of the Encyclopaedia Britannica's entry (vol. 19 p. 993) on "Octopus" spends half of its space split between two topics - defending Victor Hugo's depiction of the octopus in Toilers of the Sea and discussing the hectocotylus, the sometimes detachable sperm-carrying arm of the male octopus:

[...] The celebrated account of the octopus given by Victor Hugo in his Travailleurs de la mer is not so fictitious as some critics with a knowledge of natural history have maintained. It is true that the great French author has made the mistake of using the name Cephaloptera, which belongs to a large tropical fish similar to a skate, instead of Cephalopoda, and that he applies the term devil-fish, which belongs to Cephaloptera, to the octopus. His description is exaggerated, imaginative and sensational; but it is correct in its most important particulars, and bears evidence that the author was to some extent personally acquainted with the animal and its habits, although he was not a scientific observer. The octopus feeds on crabs, and crabs feed on carrion, and, therefore, there is nothing impossible in Hugo's account of the skeleton of a drowned man surrounded by the shells of numbers of crabs which the octopus had devoured. Whether an octopus would attack and kill a man is another question, but it certainly might seize him with its arms and suckers while holding to the rocks by other arms, and a man seized in this way when in the water might be in danger of being drowned.

[...] The separation of one of the arms of the male for purposes of reproduction is one of the most remarkable peculiarities of the Octopoda. It does not occur, however, in octopus nor in many other members of the group. One arm is always considerably modified in structure and employed in copulation, but it is only in three genera, one of which is Argonauta, that the arm spontaneously separates. The detached arm is found still alive and moving in the mantle cavity of the female, and when first discovered in these circumstances was naturally regarded by the older naturalists as a parasite. Cuvier, on account of the numerous suckers of the detached arm, gave it the name Hectocotylus (hundred suckers). When the arm is not detached but only altered in structure it is said to be hectocotylized. The extremity of this arm is expanded and assumes the shape of a spoon. Whether detached or not the modified arm possesses a cavity into which the spermatophores are passed and the arm serves to convey them to the mantle cavity of the female.

Most of the rest of the entry is devoted to specific examples of the octopus disrupting the English lobster industry.

Compare the woodcut illustration of the octopus from the World Book entry above to the bottom right specimen in the color plate below from the 1921 Encyclopedia Americana; I highly suspect they were based on the same illustration.

The Encyclopedia Americana's entry on the octopus can be found in volume 20, on page 575, with a color plate inserted just before that page and another illustrative plate inserted between pages 576 and 577. This entry does a far better job of describing the octopus itself without becoming sensationalist:

OCTOPUS, a genus of the dibranchiate Cephalopoda (q.v.), or cuttlefishes, forming the type of the family Octopodidæ, the members of which group are familiarly known as "poulpes." These forms possess eight arms of equal length, united to each other by a web varying in extent in different forms. The arms possess two rows of sessile, wholly fleshy suckers. The prominent head is joined to the body by a distinct "neck," and the body itself is short, generally more or less rounded in shape and unprovided with side or lateral fins. The shell is internal, and is represented by two short "styles," which lie imbedded in the "mantle." In the octopods the third right arm of the male animals becomes developed to form a "hectocotylus" or sexual organ (see Argonaut); and in some this modified arm is detached from the body and deposited within the mantle cavity of the female for the purpose of fertilizing the eggs, a fresh arm being developed as occasion requires.

The poulpes attained a popular notoriety from the tales which were formerly circulated of gigantic members of this group which had no existence in reality. Some forms spread their limbs 12 or 14 feet, like great spiders, and might, under favorable circumstances, hold under water a person whom they had seized until he had drowned, at the same time biting him with their horny parrot-like jaws; no doubt such accidents have occasionally happened to pearl-divers and the like. Ordinarily, however, the octopus does not attain one-half these dimensions and many species have bodies no larger than an ordinary pear. These animals live in rocky places along shore and about reefs, protecting their soft bodies by sitting in holes and crevices with arms reaching out to seize their victims, which are fishes and any animal they are able to overpower. They are themselves preyed upon by large fishes, turtles, etc. Many species are eaten in various parts of the world and the common one (Octopus vulgaris), of the Mediterranean and neighboring Atlantic coasts, has been speared and taken to market from a time immemorial, and is still a regular object of pursuit, especially in Italy. A deep-water species (Eledone moschata) is trapped for market in from 10 to 20 fathoms of water by lowering earthen jars and leaving them a few hours. The creatures creep into these jars, as a fine hiding-place, and allow themselves to be drawn to the surface. The flesh is eaten boiled, fried and in salads and is preserved by pickling. Sepia (q.v.) is the substance in the "ink-bag": and "cuttlebone" the supporting calcareous plate beneath the skin of certain species. Of the American species O. bairdii and otehrs of the eastern coast dwell in deep water or about the tropical coral reefs. On the Pacific Coast several species are taken near shore and were always utilized by the Indians. Since the settlement of California their flesh is regularly supplies to the San Francisco market, where it is bought by Italians and Chinese. Some specimens brought in there are among the largest known, measuring 14 feet across the outstretched arms. Consult books of conchology, especially Cooke, 'Mollusca' (1895); and 'Standard Natural History' (Vol. I, 1884). See Argonaut; Cephalopoda; Cuttlefish.

The German-language encyclopedia Bilder-Conversations-Lexikon für das deutsche Volk by Brockhaus, published in 1841, features a short, but thorough article (vol. 4, pp. 436-437) on the Tintenfisch ("ink fish"), a term which encapsulates the cuttlefish, squid, and octopus under a single heading (translation follows):

Tintenfisch, lat. Sepia, heißt eine Gattung Weichthiere, welche zwei große, fast verständig aussehende Augen, einen hornartigen Schnabel und um diesen acht oder zehn große Fangarme mit Saugnäpfen haben. Am Bauche haben sie einen Beutel mit einer schwarzbraunen Flüssigkeit, welche sie willkürlich von sich lassen, um das Wasser zu trüben. Mehre Arten haben unter der Haut des Rückens eine knochige Platte. Man brennt dieselbe weiß, verkauft sie unter dem Namen weißes Fischbein oder Walfischschuppe (lat. os sepiae) und benutzt sie zum Abreiben und Glätten verschiedener Gegenstände. Der hier abgebildete sogenannte Meerpolyp, der Polypus oder Octopus der Alten, hat acht Arme und findet sich zwischen Klippen in den europ. und amerk. Meeren. Seine Arme benutzt er, um sich seiner Beute zu bemächtigen und damit beim Schwimmen zu rudern und um sich auf dem Meeresboden und selbst auf dem Lande fortzubewegen. Die hier noch besonders abgebildeten Saugnäpfe an den Armen wirken ganz wie Schröpfköpfe, indem sie sich luftdicht an die Gegenstände anlegen und dann nach innen eine luftleere Höhlung bilden. Mit denselben kann sich das Thier so fest anheften, daß man ihm die Arme abschneiden muß, um es abzulösen. Es macht besonders auf Krebse Jagd. Merkwürdig ist seine Eigenschaft, seine gewöhnlich rosenrothe Farbe verändern zu können. In einigen Gegenden pflegt man diese Polypen zu essen. Sie werden etwa 6 F. groß, doch erzählt der röm. Naturforscher Plinius von einem derartigen Thiere, welchces 30 F. lange Arme gehabt hätte, die so dick gewesen wären, daß sie ein Mann kaum zu umspannen vermocht. — Der gemeine Tintenfisch, vorzugsweise Sepia genannt, auch Tintenschnecke oder Blackfisch, wird nur über 1 F. lang. Er hat acht kurze Arme und zwei längere Fühler und wird besonders in mittelländ. Meere gefunden. Seine Haut ist röthlich, mit braunen Flecken besetzt. In dem daumenlangen Tintenbeutel befindet sich die braune Flüssigkeit, welche unter dem Namen Sepia als Malerfarbe geschätzt ist. Das Weibchen legt eine Menge Eier, welche traubenförmig aneinander hangen, und daher Seetrauben (lat. uvae maritimae) genannt werden. Auch liefert besonders dieser Tintenfisch das os sepiae. Er ist, wie der Meerpolyp, genießbar. — Der braune Saft der Tintenfische mit Biester vermischt, wurde zuerst von Seydelmann zu Zeichnungen, sogenannten Sepiazeichnungen, benutzt, welche großen Beifall fanden.

Tintenfisch (Latin: sepia) is the name of a genus of mollusks, which have two large, almost intelligent-looking eyes, a horn-like beak, and, surrounding this, eight or ten long tentacles with suction cups. They have a sack on their abdomen filled with a dark-brown liquid, which they can release at will in order to cloud the water. Many varieties have a bony plate under the skin of their back. This can be burned white and sold under the name of "whalebone" or "whale scales" (Latin: os sepiae); they are used for scrubbing and polishing various objects. The so-called ocean poulp, the "polypus" or "octopus" of the ancients, pictured here, has eight arms and can be found in the crags of the European and American seas. It uses its arms to seize its prey, to steer while swimming, and to move itself on the seafloor and even on land. The suction cups on the arms, specially illustrated here, work entirely like cupping glasses, in that they lay airtight onto objects and then create a vacuous cavity inside. The animal can hold on so tightly with these that its arms must be cut off in order to remove it. It particularly likes to hunt crabs. Remarkably, it has the ability to change its normally-pink coloring. In some areas, it is common to eat these poulpes. They grow to about 6 feet [note: I am not sure exactly how long a "foot" here refers to], though the Roman naturalist Pliny tells of a similar animal which supposedly had 30 feet long arms, which were so thick, that a man could barely wrap his arms around them. — The Common Tintenfisch, preferably called sepia [cuttlefish], but also "ink slug" or "black fish" [both of these terms mean cuttlefish], is little more than 1 foot long. It has eight small arms and two longer antennae and are particularly common in the Mediterranean Sea. Its skin is reddish with brown spots. Inside of its thumb-long ink sack is a brown liquid which is treasured as the painter's color sepia. The female lays a large number of eggs, which hang on one another like grapes, and so they are called "sea grapes" (Latin: uvae maritimae). The cuttlebone is particularly common in this Tintenfisch. It is, just like the octopus, edible. — The brown juice of the Tintenfisch, when mixed with colostrum, was first used by Seydelmann for drawing so-called "Sepia Drawings", which were met with great acclaim.

Finally, to end, here are a few fun octopus facts taken from a more modern entry, specifically from the 1992 World Book (vol. 14, pp. 678-679):

• The octopus has three hearts, two of which are specifically linked to its gills.
• The octopus is able to grow a new arm if it loses one.
• The female octopus can lay over 100,000 eggs, though many of these get eaten by other animals.