Do you know ghouls from goblins and ghosts?
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.
"clergyman," c.1500, from reverend (adj.).
the ordinary English prefix of written address to the names of ministers of most Christian denominations. In the 15th century it was used as a general term of respectful address, but it has been habitually used as a title prefixed to the names of ordained clergymen since the 17th century. In the Church of England, prefects apostolic who are not in episcopal orders (e.g., deans, provosts, cathedral canons, rectors of seminaries and colleges, and priors and prioresses) are addressed as "very reverend." Bishops, abbots, abbesses, and vicars-general are addressed as "right reverend," and archbishops and (in Roman Catholicism) cardinals are addressed as "most reverend." The moderator of the Church of Scotland is also styled "right reverend." Carthusians use the title "reverend" only for their prior-general; all other Carthusian priests are styled "venerable father." While, strictly speaking, the term is an adjective to be followed by "Doctor" or "Mister," its common usage has made it a noun.