a hard, square, ceremonial hat with three or four vertical projections and sometimes with a pompom or tassel at the top, worn by Roman Catholic clergy
Origin of birettaItalian berretta from Late Latin birrettum, diminutive of Classical Latin birrus, a hood, cloak, probably from Celtic base, as in Cymric byrr, Middle Irish berr, short
A stiff square cap with three or four ridges across the crown. Birettas are worn especially by Roman Catholic clergy and are black for priests, purple for bishops, and red for cardinals.
Origin of birettaItalian berretta from Old Provençal berret cap from Late Latin birrus hooded cloak probably of Celtic origin perhaps akin to Irish berr Welsh byrr short
Gerhard Ludwig Müller
From Italian 'biretta'