reverend (adj.)youdaoicibaDictYouDict[reverend 词源字典]
early 15c., "worthy of respect," from Middle French reverend, from Latin reverendus "(he who is) to be respected," gerundive of revereri (see reverence). As a form of address for clergymen, it is attested from late 15c.; earlier reverent (late 14c. in this sense). Abbreviation Rev. is attested from 1721, earlier Revd. (1690s). Very Reverend is used of deans, Right Reverend of bishops, Most Reverend of archbishops.[reverend etymology, reverend origin, 英语词源]
reverend (n.)youdaoicibaDictYouDict
"clergyman," c. 1500, from reverend (adj.).