Penguin
late 16th century (originally denoting the great auk): possibly of Welsh origin, from pen gwyn ‘white head’.
wiktionary
Unknown; [1] first attested in the 16th century in reference to the auk of the Northern hemisphere; the word was later applied to the superficially similar birds of the Southern hemisphere (as was woggin). Possibly from Welsh pen(“head”) and gwyn(“white”), or from Latin pinguis(“fat”). See citations and the Wikipedia page.
etymonline
penguin (n.)
1570s, originally used of the great auk of Newfoundland (now extinct; the last two known birds were killed in 1844); the shift in meaning to the Antarctic swimming bird (which looks something like it, observed by Drake in Magellan's Straits in 1578) is from 1580s. The word itself is of unknown origin, though it often is asserted to be from Welsh pen "head" (see pen-) + gwyn "white" (see Gwendolyn). The great auk had a large white patch between its bill and eye. The French and Breton versions of the word ultimately are from English. A similarity to Latin pinguis "fat (adj.), juicy," figuratively "dull, gross, heavy," has been noted.
