waterfowl, natatorial bird of the family Anatidae, Old English duce (found only in genitive ducan) "a duck," literally "a ducker," presumed to be from Old English *ducan "to duck, dive" (see duck (v.)). Replaced Old English ened as the name for the bird, this being from PIE *aneti-, the root of the "duck" noun in most Indo-European languages.
In the domestic state the females greatly exceed in number, hence duck serves at once as the name of the female and of the race, drake being a specific term of sex. [OED]
As a term of endearment, attested from 1580s (see ducky). duck-walk, a squatting waddle done by a person, in imitation of a duck, is by 1915; duck soup, slang for "anything easily done," is by 1899. Duck's ass haircut is from 1951. Ducks-and-drakes, skipping flat stones on water, is from 1580s; the figurative sense of "throwing something away recklessly" is c. 1600.
"a large waterfowl proverbially noted, I know not why, for foolishness" [Johnson], Old English gos "a goose," from Proto-Germanic *gans- "goose" (source also of Old Frisian gos, Old Norse gas, Old High German gans, German Gans "goose"), from PIE *ghans- (source also of Sanskrit hamsah (masc.), hansi (fem.), "goose, swan;" Greek khen; Latin anser; Polish gęś "goose;" Lithuanian žąsis "goose;" Old Irish geiss "swan"), probably imitative of its honking.
Geese are technically distinguished from swans and from ducks by the combination of feathered lores, reticulate tarsi, stout bill high at the base, and simple hind toe. [Century Dictionary]
Spanish ganso "goose" is from a Germanic source. Loss of "n" sound before "s" is normal in English (compare tooth). Plural form geese is an example of i-mutation. Meaning "simpleton, silly or foolish person" is from early 15c. To cook (one's) goose is attested by 1845, of unknown origin; attempts to connect it to Swedish history and Greek fables are unconvincing. Goose-egg "zero" is attested by 1866 in baseball slang, from being large and round. The goose that lays golden eggs (15c.) is from Aesop.