A great variety of titles and terms of address exist relative to those who occupy places of religious leadership, especially those who preach or hold ecclesiastical office. Members of the Roman Catholic (and to a great extent, Episcopal) Church employ such terms as the following: reverend/father (at the parish priest level), most holy father (the pope), your eminence, your excellency, most reverend, right reverend, reverend monsignor, and others. Protestants almost universally employ reverend for their preachers. Rabbi is the common title in Judaism. Freemasonry applies variations of worshipful master to its hierarchy.
The origins of such titles would likely be interesting and perhaps entertaining. All that matters to devout Bible students, however, is what, if anything, the Bible says about them, which indeed it does, both explicitly and implicitly.
In a scathing rebuke, Jesus chastised the hypocrisy and egotism of the scribes and Pharisees (Jewish religious leaders), for seeking places of prominence and to be called “Rabbi.” He then instructed the crowd (including the apostles):
But be not ye called Rabbi: for one is your teacher, and all ye are brethren. And call no man your father on the earth: for one is your Father, even he who is in heaven. Neither be ye called masters: for one is your master, even the Christ (Mat. 23:6–10; emph. DM).
Note first that he was not referring to titles or modes of address in business, secular, or family relationships, but to religious titles specifically. Note second that Jesus named three of the very titles mentioned earlier (i.e., father, rabbi, master), forbidding even His apostles to arrogate these to themselves. To assume such titles and allow/expect others to so address them—in whatever age—equals rebellion to an explicit order of the Son of God. Moreover, they thereby take to themselves honors/titles mere men are not permitted to accept.
The New Testament also addresses the wearing of religious titles implicitly. James and John, two of the apostles, once sought places of prominence and power in Jesus’ kingdom (the nature of which they utterly misconstrued). Jesus then lectured the Twelve on the need to humbly serve rather than to seek exaltation. All of the numerous titles (read them again) are designed to exalt and glorify rather than to express service and humility (e.g., reverend means one revered). The New Testament knows nothing of “clergy/laity” distinctions, which all such titles both signal and perpetuate. Gospel preachers/evangelists are simply Christians who choose to give their lives to preaching.