advocate:  Etymologically, advocate contains the notion of ‘calling’, specifically of calling someone in for advice or as a witness. This was the meaning of the Latin verb advocāre (formed from vocāre ‘call’, from which English also gets vocation). Its past participle, advocātus, came to be used as a noun, originally meaning ‘legal witness or adviser’, and later ‘attorney’.
In Old French this became avocat, the form in which English borrowed it; it was later relatinized to advocate. The verb advocate does not appear until the 17th century. The word was also borrowed into Dutch, as advocaat, and the compound advocaatenborrel, literally ‘lawyer’s drink’, has, by shortening, given English the name for a sweetish yellow concoction of eggs and brandy. => invoke, revoke, vocation
mid-14c., "one whose profession is to plead cases in a court of justice," a technical term from Roman law, from Old French avocat "barrister, advocate, spokesman," from Latin advocatus "one called to aid; a pleader, advocate," noun use of past participle of advocare "to call" (as witness or advisor) from ad- "to" (see ad-) + vocare "to call," related to vocem (see voice (n.)). Also in Middle English as "one who intercedes for another," and "protector, champion, patron." Feminine forms advocatess, advocatrice were in use in 15c.