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" (from PIE *wes- (2) "to clothe," extended form of root *eu- "to dress."). 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).