Meaning

noun the overhead upper surface of a covered space

noun (meteorology) altitude of the lowest layer of clouds

noun an upper limit on what is allowed

originFrom Middle English celing (“paneling; (bed) cover or hanging”), from celen (“to cover or panel walls”) (from Old French celer (“to conceal”)) + -ing (gerund-forming suffix). By surface analysis, ceil + -ing.

Etymology from Wiktionary, CC BY-SA 3.0