Pliny the Elder [1st century CE] (Natural History, Book 9, 46; Book 9, 48): [Book 9, 46] There are many sorts of polyp. The land kinds are larger than the marine. They use all their arms as feet and hands, but employ the tail, which is forked and pointed, in sexual intercourse. The polyps have a tube in their back through which they pass the sea-water, and they shift this now to the right side and now to the left. They swim with their head on one side, this while they are alive being hard as though blown out. Otherwise they remain adhering with a kind of suction, by means of a sort of suckers spread over their arms: throwing themselves backward they hold on so that they cannot be torn away. They do not cling to the bottom of the sea, and have less holding-power when full-grown. They alone of the soft creatures go out of the water on to dry land, provided it has a rough surface: they hate smooth surfaces. They feed on the flesh of shellfish, the shells of which they break by enfolding them with their tentacles; and consequently their lair can be detected by the shells lying in front of it. And though the polyp is in other respects deemed a stupid animal, inasmuch as it swims towards a man's hand, it has a certain kind of sense in its domestic economy: it collects everything into its home, and then after it has eaten the flesh puts out the refuse and catches the little fishes that swim up to it. It changes its color to match its environment, and particularly when it is frightened. The notion that it gnaws its own arms is a mistake, for this is done to it by the congers ; but the belief that its tails grow again, as is the case with the gecko and the lizard, is correct. [Book 9, 48] One variety of the polypus kind is the stink-polyp, named from the disagreeable smell of its head, which causes it to be the special prey of the lamprey. Polyps go into hiding for periods of two months. They do not live more than two years; but they always die of consumption, the females more quickly and usually as a result of bearing offspring. ... Shell-fish do not possess sight or any other sense except consciousness of food and danger. Consequently the polyps lie in wait for the shell-fish to open, and placing a stone between the shells, not on the fish's body so that it may not be ejected by its throbbing, thus go to work at their ease, and drag out the flesh, while the shell-fish try to shut up, but in vain, as they are wedged open: so clever are even the most stupid of animals.- [Rackham translation]

Isidore of Seville [7th century CE] (Etymologies, Book 12, 6:44): The octopus (polypus), that is, ‘with many feet’, for it possesses many tentacles. This ingenious animal reaches for the hook and grasps it with its arms, not biting it, and it does not release the hook until it has eaten around the food on it. - [Barney, Lewis, et. al. translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Marine monsters 6.42; Fish 7.55): [Thomas describes the octopus under the names polypus (marine monster) and multipes (fish).] [Marine monsters 6.42] An octopus is a fish, as Pliny says, which uses its feet as arms. This animal has such strength in its arms that it sometimes seizes by force a sailor standing carelessly on a ship and drags him into the sea, and is satisfied with his flesh: for it eats meat gladly. They are most numerous in the sea near Venice. It has a forked tail and a sharp pipe on its back, through which it sends sea water, and transfers the tube to the right and to the left when it wills. It swims with its head to the side; its head is hard. They stick to the rocks on their backs, so that they cannot be pulled off. They are the only fish to come onto dry land. Octopuses come together in the winter and give birth in the spring. Octopuses come together with their heads turned to the ground. Octopuses sit on their eggs and incubate as if they make a chamber with their arms. An octopus cannot be plucked from a stone; but if a stinking thing is brought to it, it immediately recoils from the smell. They feed on the meat of shellfish, which they break apart. They leave the shells in front of them, thus revealing their resting place. With this this they also they deceive the shellfish: the shellfish lack sight and sense beyond that they detect food and flee from dangers. And so, until the shell is open, the octopus lies in wait. But when they find a rock, as Pliny and Ambrose and the great Basil say, they fasten themselves tenaciously and from that rock make a shelter for themselves to hide from fish, and thus they catch the fish and extract the flesh. Octopuses hide for two months, and do not live beyond two years. But they perish by wasting, and females always more quickly, because they give birth. [Fish 7.55] Multipes [octopus], as Pliny says, is a marine fish, having its name from the fact that as many terrestrial animals have many feet, so also this. Those feet go out from the side. This fish congregates in the winter, and among the other fish builds a nest for itself out of shoots. But the great Basil says that it places an egg in the nest that is warmed by the water, and produces offspring from it. They lay eggs for two months, but one egg only, and this as small as a nut. And after the female has laid the egg, she sits for forty nights and nurtures it, and in the ensuing time innumerable offspring are made from it. And it is necessary that they produce many offspring, because if this were not the case, their species would be greatly diminished, because they consume each other themselves, and it is an animal that eats a lot. However, the animal is very weak and deteriorates quickly, and this perhaps because of too much food. Aristotle: The head of the male is longer than the head of the female. When the female ovulates, she becomes very weak because of excessive laying and because she does not feed at that time and is not sated with food. Many lobsters [karabao] can overcome the sea monster, which is nevertheless strong and robust. But the octopus overcomes the lobster more by cunning than by strength; and this is the evidence that the octopus overcomes it, because sometimes, while they are found together caught in the net, the lobster is frequently found dead or mortally wounded. And in this it is given to understand that wisdom is more valuable than strength, and victory is not given by virtue, but from heaven. There is a certain kind of octopus, which being naturally cunning, in order that the shell of its back may be hard and able to withstand the salt waters of the sea and the adverse effects of the rocks, it swims on the surface of the water, and exposes the shell of its back to the sun, that it may dry up and become harder. - [Badke translation/paraphrase]