The meaning of INNER SANCTUM is a very private room or place —often used figuratively.

a private place or room where someone is never interrupted: To see inside one of these rooms is to get a glimpse into the gamer's inner sanctum.

The Latin phrase sanctum sanctorum is a translation of the Hebrew term קֹדֶשׁ הַקֳּדָשִׁים (Qṓḏeš HaQŏḏāšîm), literally meaning Holy of Holies, which generally refers in Latin texts to the holiest place of the Ancient Israelites, inside the Tabernacle and later inside the Temple in Jerusalem, but the term also has some derivative use in application to imitations of the Tabernacle in church architecture.

INNER SANCTUM definition: 1. a private place or room where someone is never interrupted: 2. a private place or room where….