SANCTUM
sanctum, sanctum sanctorum
(noun) a place of inviolable privacy; “he withdrew to his sanctum sanctorum, where the children could never go”
Source: WordNet® 3.1
Etymology
Noun
sanctum (plural sanctums)
A place set apart, as with a sanctum sanctorum; a sacred or private place; a private retreat or workroom.
Source: Wiktionary
Sanc"tum, n. Etym: [L., p.p. of sanctire to consecrate.]
Definition: A sacred place; hence, a place of retreat; a room reserved for
personal use; as, an editor's sanctum. Sanctum sanctorum Etym: [L.] ,
the Holy of Holies; the most holy place, as in the Jewish temple.
Source: Webster’s Unabridged Dictionary 1913 Edition