1570s, "holy place of the Jewish tabernacle," from Latin sanctum "a holy place," as in Late Latin sanctum sanctorum "holy of holies" (translating Greek to hagion ton hagiou, translating Hebrew qodesh haqqodashim), from neuter of sanctus "holy" (see saint (n.)). In English, sanctum sanctorum attested from c. 1400; in the sense of "a person's private room or retreat" it is attested by 1706.
I had no need to make any change ; I should not be called upon to quit my sanctum of the school-room — for a sanctum it was now become to me —a very pleasant refuge in time of trouble. ["Jane Eyre"]
updated on December 08, 2021