Adytum
Watson's Biblical & Theological Dictionary [1]
is a Greek word, signifying inaccessible, by which is understood the most retired and secret place of the Heathen temples, into which, none but the priests were allowed to enter. The adytum of the Greeks and Romans answered to the sanctum sanctorum of the Jews, and was the place from whence oracles were delivered.
Webster's Dictionary [2]
(n.) The innermost sanctuary or shrine in ancient temples, whence oracles were given. Hence: A private chamber; a sanctum.
Cyclopedia of Biblical, Theological and Ecclesiastical Literature [3]
(from Ἄδυτον , Inaccessible), the Shrine or inner room of a sacred building; hence applied in later times to the penetralia of the Temple at Jerusalem, which were accessible to the priests alone, especially the sanctuary, or
"holy place," and still more to the "holy of holies," or inmost chamber. Ecclesiastical writers also employ it metaphorically to denote the recesses of the heart or spiritual nature, and sometimes to designate the deeper mysteries of divine truth. See Agion
