The vb. smouch to daub, dirty, stain, is given by Sir G. C. Lewis Gloss. Heref. (1839), s.v. smirch.
1873. Miss Broughton, Nancy, III. 192. A huge smouch of black under each of their eyes.
1882. G. P. Lathrop, in Harpers Mag., Aug., 379/1. They keep carefully away from the smouch of the cigarette trays.