The classical Latin phrase 'Sanctum Sanctorum' means literally "Holy of Holies." It was originally applied in a religious context to the most sacred place within a sacred building, such as a temple. However, in common usage can also be applied to mean any reserved, private, or much-valued place.
'Sanctum Santorum' has two meanings:
1.) Holy Shit
2.) That most precious and sacred place in your body where one may find Santorum
You are disapprovingly describing an acquaintance who acts like a slut. "He doesn't treat his body like a temple. His Sanctum Santorum is anyone's for the asking."
2. the anus when smeared with santorum, a term popularized by sex columnist Dan Savage and his readers.
3. the home of Senator Rick Santorum (R-Pa.)