Rabbi
The title rabbi, used for religious teachers in Judaism, simply means “great” in Hebrew. But the same word also means “nobleman” & “usurer”. Many famous spooks allegedly come from a long line of “rabbis” — such as the ultra-wealthy industrial clans around fake communist Karl Marx. What the spooks really mean is probably that they come from a long line of aristocrats & bankers.
The common basic meaning of the word root רב rb is “enlarge” or “great”, the other meanings are derived from that. Noblemen are the politically “enlarged” people, and usurers “enlarge” their capital through interest. For the actual teachers & rabbis, it was probably a honorific title, such as “o great one”.
Such actual rabbis do exist too, I suppose, just like actual common-birth priests of other confessions exist, among the lower ranks.
Hebrew, Aramaic, Syriac, Persian rby = increase, interest, usury, usurer
רבה ; רבי rby; rbh : to be much, many; to grow, increase; to lend; borrow on usury; to make a profit; to cause increase — Hebrew (Jastrow)
רבי rby : to increase; to grow in number or amount; to accrue interest; to lend to someone at interest; to profit by someone; to be augmented by interest — Aramaic (CAL)
רבי rby rabbay : usurer; nurturer; captain (?) — Aramaic (CAL)
רביני rbyny rebbyanay : of interest, usurious — Aramaic (CAL)
רבי rby rebbay : interest — Aramaic (CAL)
רבית rbyt ribit : interest (price of credit) — Hebrew (Wikt)
ܪܲܒܵܝ rby rabbai : an usurer, a loan shark / gombeen man, one who loans money at an exorbitant rate, an (unfair) moneylender — Syriac (AAF)
ربا rbˀ ribaʼ : profit on goods; usury — Persian (Steingass)
ربا rbˀ reba : usury; (unlawful) profit — Persian (Sulayman)
Hebrew, Aramaic rb = great, teacher, master, lord, nobleman
רבא rbˀ : large, great, important — Hebrew (Klein)
רבב rbb : to be great; to be a teacher, be in office — Hebrew (Jastrow)
רב rb : captain, chief, great, lord, master, stout — Aramaic (Strong)
רב rb : large, great, numerous; senior; chief, master, teacher; school, academy — Hebrew (Jastrow)
רב rb : lord, chief; master; teacher; ‘rabbi’; cp. Aram.-Syr. רַב, רַבָּא (= prince, chief, captain, master, teacher), Ugar. rb (= chief), Akka. rabu (= chief). Arab. rabb (= lord, God) is probably an Aram. loan word. — Hebrew (Klein)
רב rb : chief; teacher; nobleman, chieftain; master; teacher; in direct address: rabbī: my master, teacher, rabbi; rbn: our master — Aramaic (CAL)
רבן rbn : lord, master; chief, head man; abbot; scholar, teacher — Aramaic (CAL)