sanctum (noun) – a sacred or private place; a retreat
BREAKDOWN: SANCT- (sacred or holy) + -UM (structure)
— sanctum sanctorum describes the holy of holies, either a place of special sacredness or an individual’s most private retreat or sanctuary
This word is built on the root SANCT-, which means sacred or holy.
Common SANCT- words include include saint and sanctuary.
More esoteric SANCT- words include sanctificate, sanctity, and sanctiloquence.