biretta (n.)

type of flat cap, 1828, from French barrette, cognate with Spanish birreta, Italian beretta (see biretta).

also berret, "round, flat, woolen cap," originally worn by Basque peasants, 1827 as a fashionable accessory, from French béret, 19c., from dialect of Béarn, from Old Gascon berret "cap," from Medieval Latin birretum, diminutive of Late Latin birrus "a large hooded cloak," a word perhaps of Gaulish origin. For the clerical version, see biretta.