means Regarded as holy, set apart for or deserving of religious reverence — or, more loosely, something treated as too important or precious to be violated.

from From Latin sacer, 'holy, consecrated' — but also, tellingly, 'accursed, forbidden,' since what was given over to the gods was withdrawn from ordinary human use entirely. The same root gives us sacrifice (literally 'to make sacred'), sacrament, and sacrilege. English took it via the past participle sacrare, 'to make holy,' and that double edge — devoted and untouchable, blessed and dangerous — was baked in from the very start.