First attested about 1860, in the US, as a fanciful alteration of lick and the verb split. lick appears to have something to do with animals made to go faster by means of a "lick" of a whip, although it may have also originated due to a preference for rapid licking (the "quick lick").
Audio (US) (file)
- Quickly; as fast as possible; in short order.
- At the sound of the starting gun, they were off and running lickety-split.
- “lickety-split” in Douglas Harper, Online Etymology Dictionary (2001).