bellow (v.)youdaoicibaDictYouDict[bellow 词源字典]
apparently from Old English bylgan "to bellow," from PIE root *bhel- (4) "to sound, roar." Originally of animals, especially cows and bulls; used of human beings since c. 1600. Related: Bellowed; bellowing. As a noun from 1779.[bellow etymology, bellow origin, 英语词源]