baayoudaoicibaDictYouDict[baa 词源字典]
imitative sound of a sheep, attested from 1580s, but probably older, as baa is recorded before this a name for a child's toy sheep. Compare Latin bee "sound made by a sheep" (Varro), balare "to bleat;" Greek blekhe "a bleating;" Catalan be "a sheep."[baa etymology, baa origin, 英语词源]