vestry (n.)
mid-15c., probably from Anglo-French *vesterie, from Old French vestiaire "room for vestments, dressing room" (12c.), from Latin vestarium "wardrobe," noun use of neuter of vestiarius (adj.) "of clothes," from vestis "garment" (see vest (v.)). Often also a meeting room for the transaction of parish business, and retained in non-liturgical churches as the name of a separate room used for Sunday school, prayer meetings, etc., hence transferred secular use (as in vestryman, 1610s).