What is the prefix and prefix meaning of advocate?

One who pleads the cause of another. Specifically: One who pleads the cause of another before a tribunal or judicial court; a counselor., One who defends, vindicates, or espouses any cause by argument; a pleader; as, an advocate of free trade, an advocate of truth., Christ, considered as an intercessor., To plead in favor of; to defend by argument, before a tribunal or the public; to support, vindicate, or recommend publicly., To act as advocate.