Rabbi
late Old English, via ecclesiastical Latin and Greek from Hebrew rabbī ‘my master’, from raḇ ‘master’.
wiktionary
From Middle English raby, from Ecclesiastical Latin rabbi, and its source Koine Greek ῥαββί(rhabbí), from (post-Tanakh) Hebrew רַבִּי (rabbi, “my master”), from רַב (rav, “master [of]”) + ־י (-i, “me”). Compare late Old English rabbi.
etymonline
rabbi (n.)
"Jewish doctor of religious law," early 14c. (in late Old English in biblical context only, as a form of address); in Middle English as a title prefixed to personal names, also "a spiritual master" generally; from Late Latin rabbi, from Greek rhabbi, from Mishnaic Hebrew rabbi "my master."
This is formed from -i, first person singular pronominal suffix, + rabh "master, great one," title of respect for Jewish doctors of law. This is from the 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").
