breath n.

Old English bræð "odor, scent, stink, exhalation, vapor" (the Old English word for "air exhaled from the lungs" was æðm), from Proto-Germanic *bræthaz "smell, exhalation" (source also of Old High German bradam, German Brodem "breath, steam"), perhaps [Watkins] from a PIE root *gwhre- "to breathe; smell." The original long vowel (preserved in breathe) has become short.

The meaning "ability to breathe," hence "life" is from c. 1300. The meaning "a single act of breathing" is from late 15c.; the sense of "the duration of a breath, a moment, a short time" is from early 13c. The meaning "a breeze, a movement of free air" is from late 14c.