From Latin 'caelestis' (heavenly), from 'caelum' (sky) — carrying both astronomical and spiritual meanings since antiquity.
Relating to the sky or outer space; of or resembling heaven; supremely good or beautiful.
From Old French 'celestiel,' from Latin 'caelestis' (heavenly, of the sky), from 'caelum' (sky, heaven). The origin of Latin 'caelum' is debated: it may derive from Proto-Indo-European '*keh₂id-' (bright, clear) or from '*ḱel-' (to cover, to conceal), the sky being conceived either as the bright space above or as the covering over the earth. The dual meaning — both astronomically 'of the sky
The word 'ceiling' may be related to 'celestial' through Latin 'caelum' (sky). In medieval English, 'ceiling' originally meant an interior sky — the panelling or plaster that covered the underside of a roof, creating an artificial heaven above one's head. The indoor sky became so familiar that we forgot its cosmic origin.