hat

English hat comes from Middle English hat, from Old English hætt, from Proto-Germanic *hattuz. Some trace this further back to a Proto-Indo-European root meaning 'to guard, cover, care for, protect,' though it may instead be a wanderwort that spread between languages rather than descending in a single line.

The word has stayed remarkably steady across Germanic languages, keeping its basic meaning of head covering from Old English straight through to today.

It's cognate with Swedish and Norwegian hatt, Icelandic hattur, and Finnish hattu, all meaning 'hat.' It's also related to the English word hood, and distantly to Latin cassis ('helmet') and Persian xud ('helmet'), if the guarding root is correct.