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").
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- 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, 2001–2017.