late 14c., "unable to breathe," from breath + -less. Meaning "out of breath, panting" is from mid-15c. Also used from 1590s in the sense "dead." Meaning "forgetting to breathe" due to excitement, awe, anticipation, etc. is recorded from 1765. Related: Breathlessly; breathlessness. Breathful was used late 16c.
updated on October 14, 2021