the.com/advocate

means A person who speaks or argues in support of someone or something, often professionally, as in law or a cause.

from From Latin 'advocare' — 'ad' (to) plus 'vocare' (to call) — literally 'to call to one's aid.' In Roman courts, an advocatus was the person you summoned to stand beside you and speak on your behalf. The word kept that sense of being called in as reinforcement as it moved through Old French 'avocat' into English.