octopus
n.
1758, genus name of a type of eight-armed cephalopod mollusks, from Greek oktopous, literally "eight-footed," from okto "eight" (see eight) + pous "foot" (see foot, n.). Proper plural is octopodes, though octopuses probably works better in English. Octopi is from mistaken assumption that -us in this word is the Latin noun ending that takes -i in plural.
〔李〕n.章鱼属动物 [pus( ←pod)=foot] ←octa-,octo-[GK] =eight八