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 "smītan" ("to daub, smear, smudge; soil, defile, pollute"): *smōcgan ("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.
smidgen (plural smidgens)
- A very small quantity or amount.
Some cookbooks and manufacturers of kitchen measurement sets have attempted to define a smidgen for recipes. Anything between 1/25 and 1/48 of a teaspoon may be found, 1/32 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 a smidgen being larger than a drop but smaller than a pinch.