c.1340, "an odor," from O.Fr. flair "odor or scent," from flairer "to smell," from L.L. fragrare "emit (a sweet) odor" (see fragrant), with shift of -r- to -l- by dissimilation. Sense of "special aptitude" is Amer.Eng. 1925, perhaps from notion of a hound's ability to track scent.
