Английский Этимологический словарь - smile (v.)

- c.1300, perhaps from M.L.G. *smilen or a Scand. source (e.g. Swed. smila "smile," from PIE base *smei-. Gradually pushed the usual O.E. word, smearcian (modern smirk), into a specific, unpleasant sense. The noun is from 1562. Romance, Celtic, and Slavic languages tend to use a dim. of the word for "laugh" to mean "smile" (cf. L. ridere "laugh;" subridere "smile"), with perhaps a literal notion of "small laugh," or "low laugh."