smid·gen also smid·geon or smid·gin 
(smĭjən)
(smĭjən)n.
A very small quantity or portion; a bit or mite: "a smidgen of genius, a sliver of cutting truth" (John Simon).
[Probably alteration of dialectal smitch, particle, perhaps ultimately from Middle English smite, perhaps from past participle of smiten, to smite; see SMITE.]