sanctum : Idioms & Phrases

• noun small evergreen tree of the southern United States and West Indies a source of lignum vitae wood
  bastard lignum vitae.
  

WordNet

• noun a place of inviolable privacy
  sanctum.
  
  • he withdrew to his sanctum sanctorum, where the children could never go
• noun (Judaism) sanctuary comprised of the innermost chamber of the Tabernacle in the temple of Solomon where the Ark of the Covenant was kept
  holy of holies.
  

WordNet

• L. , the Holy of Holies; the most holy place, as in the Jewish temple.

Webster 1913