What is the root word of advocate

Ad "toward, near" voc means voice "to speak". The root word is from Latin I think

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 ...