"to draw air into and expel it from the lungs; to inhale and exhale (a scent, etc.)," c. 1200, not in Old English, but it retains the original Old English vowel of its source word, breath. To breathe (one's) last "die" is from 1590s. To breathe down the back of (someone's) neck "be close behind" is by 1946. Related: Breathed; breathing.