octopus

Octopus goes back to Ancient Greek oktopous, recorded in classical texts by the 5th century BCE. The word joins okto, eight, with pous, foot. Greek named the animal directly from its limbs. It was a plain compound, almost a counted description.

Greek writers used oktopous for the sea creature known for its grasping arms and quick color changes. Aristotle mentions the animal in his zoological works in the 4th century BCE. The form belonged to ordinary Greek word-building, like other compounds with numbers and body parts. Nothing exotic was needed: it was simply the eight-footed one.

Latin borrowed the word as octopus, preserving its Greek shape more closely than many other loans. Learned European languages kept the classical form alive in scientific and literary use. English took octopus in the mid-18th century, especially in natural history writing. The modern debate over plurals came later because the word looks Latin but is Greek in origin.

That is why octopuses is the regular English plural, while octopodes reflects Greek and octopi imitates Latin patterning. All three forms appear in print, but octopuses has become the standard everyday choice. The singular, though, has barely changed across two millennia. A Greek counting word became a global animal name.