Beret
early 19th century: from French béret ‘Basque cap’, from Old Provençal berret, based on late Latin birrus ‘hooded cape’. Compare with biretta.
wiktionary
From French béret, from Occitan ( Gascon) berret(“cap”), from Old Occitan berret, from Medieval Latin birretum, from Late Latin birrus(“large hooded cloak”), from Gaulish birrus(“short cloak”), from Proto-Celtic *birros(“short”) (compare Welsh byr, Middle Irish berr). Compare biretta.
etymonline
beret (n.)
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.