late 14c., "fixed in place," from Old French dormant (12c.), present participle of dormir "to sleep," from Latin dormire "to sleep," from PIE root *drem- "to sleep" (cognates: Old Church Slavonic dremati "to sleep, doze," Greek edrathon "I slept," Sanskrit drati "sleeps"). Meaning "in a resting situation" (in heraldry) is from c.1500. Meaning "sleeping' is from 1620s.