Swiping in Child English

English allows a peculiar type of elliptical wh-questions that can be found only under sluicing, in which the wh-object of the preposition appears not after the preposition but before it, as in “John fixed it, but I don’t remember what with.” Merchant (2002) calls this construction Swiping. This study evaluates two competing syntactic analyses of Swiping, by using data from a novel source: the acquisition of English. The findings from child English lend support to the view that swiping crucially involves preposition-stranding in its derivation, and cast doubt on the proposal that pied-piping of a preposition plays a crucial role in the derivation of Swiping sentences.