late 14c., gaspen, of uncertain origin, perhaps from Old Norse geispa "to yawn," or its Danish derivative gispe "gasp," which probably are related to Old Norse gapa (see gape). Related: Gasped; gasping.
The moment before death; also, the end. For example, “Fight till the last gasp” (Shakespeare, 1 Henry VI, 1:2), or He was determined to stay at the party until the last gasp. This idiom alludes to taking one's last breath, literally (first example) or figuratively (second example).
[ Late 1500s