early 14c., from O.Fr. botrez "flying buttress," lit. "buttressed," pl. of boteret "support," from bouter "to thrust against," of Frankish origin (cf. O.N. bauta "to strike, beat"), from P.Gmc. *butan, from PIE base *bhau- "to strike" (see butt (v.)). The verb is from late 14c.
