sanctum sanc·to·rum 
(săngk-tôrəm)
(săngk-tôrəm)n.
1. Judaism The innermost shrine of a tabernacle and temple; the holy of holies.
2. An inviolably private place: The clubhouse was their sanctum sanctorum.
[Late Latin sānctum sānctōrum (translation of Greek to hagion tōn hagiōn, translation of Hebrew qōdeš haqqodāšîm) : sānctum, holy place + sānctōrum, genitive pl. of sānctum, holy place.]