Having a legal right to something that cannot be taken away, or wearing ceremonial robes.
From Latin vestitus, past participle of vestire 'to clothe.' Originally referred to being clothed in ceremonial garments, then extended metaphorically to being 'clothed' with legal rights or authority in the 14th century.
The financial term 'vested interest' brilliantly captures how legal rights were once literally embodied in ceremonial clothing - you wore your authority! This connection between clothing and legal status persists in judicial robes and academic regalia.
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