penguin

The origin of penguin is uncertain. It may come from Welsh pen ("head") and gwyn ("white"), or from Latin pinguis ("fat"); the word first appears in the 16th century.

The name was first used for the auk of the Northern hemisphere, then later applied to the superficially similar black-and-white birds of the Southern hemisphere now called penguins.

One theory ties penguin to Welsh gwyn ("white"), the same root behind the 'white' half of its possible name; another ties it to Latin pinguis ("fat"), making it a distant cousin of English words built on that root, though the facts don't name one directly.