"coat of arms," late 13c., from Old French blason (12c.) "a shield, blazon," also "collar bone;" common Romanic (cf. Spanish blason, Italian blasone, Portuguese brasao, Provençal blezo, the first two said to be French loan-words); of uncertain origin. OED doubts, on grounds of sense, the connection proposed by 19c. French etymologists to Germanic words related to English blaze (n.1).