rabbi (n.)

"Jewish doctor of religious law," late 15c. (in Old English in biblical context only; in Middle English also as a title prefixed to personal names), from Late Latin rabbi, from Greek rhabbi, from Mishnaic Hebrew rabbi "my master," from rabh "master, great one," title of respect for Jewish doctors of law + -i, first person singular pronominal suffix. From Semitic root r-b-b "to be great or numerous" (compare robh "multitude;" Aramaic rabh "great; chief, master, teacher;" Arabic rabba "was great," rabb "master").