- A lively or vivacious quality. Synonyms: vigor, energy, vitality, enthusiasm, etc.
- Physical attractiveness or sex appeal. Also see: it (as in "it" girl).
As far as I can tell the first one is named after the sound
associated with exertion
, the second with the sound a person makes when getting his wind
knocked out by a strong (in this case metaphorical) blow
. It's onomatopoeic
, you know