1758, genus name of a type of eight-armed cephalopod mollusks, from Gk.
oktopous "eight-footed," from
okto "eight" (see
eight) +
pous "foot." Proper plural is
octopodes, though
octopuses probably works better in English.
Octopi is from mistaken assumption that
-us is the L. noun ending that takes
-i in plural.