Origin of smidgenprobably ; from dialect, dialectal smidge, variant, variety of smitch, particle
also smid·geon or smid·gin
Origin of smidgenProbably alteration of dialectal smitch, particle, perhaps ultimately from Middle English smite, perhaps from past participle of smiten, to smite; see smite.
Some cookbooks and manufacturers of kitchen measurement sets have attempted to define a smidgen for recipes. Anything between 1/25th and 1/48th of a teaspoon may be found, 1/32nd being perhaps the most commonly used. Other commonly used measures for small amounts include tad, dash, pinch, and drop. There seems to be some consensus of tad being the largest in this set and smidgen being larger than a drop but smaller than a pinch.
Likely based on a variant of smeddum, influenced by Scots "smitch" ("stain, speck") . Confer Northumbrian dialectal English smiddum ("small particle of lead ore; smitham"). Scots "smitch" may derive from an unattested synonym of Old English "smÄ«tan" ("to daub, smear, smudge; soil, defile, pollute"): *smÅcgan ("to soil, stain, taint, blacken"). If so, then cognate with smudge.
Alternate etymology connects smidgeon with Scottish Gaelic "smidin" ("small syllable"), though this is highly improbable considering the implied semantic shift that would have to have occurred.