rabbinical adj.

"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").

compound adjectival word-forming element, usually interchangeable with -ic but sometimes with specialized sense (such as historic/historical, politic/political), Middle English, from Late Latin -icalis, from Latin -icus + -alis (see -al (1)). Probably it was needed because the forms in -ic often took on a noun sense (for example physic). Forms in -ical tend to be attested earlier in English than their twins in -ic.

"dignity or office of a rabbi," 1702, from rabbin "rabbi" (see rabbinical) + -ate (1).