Smirk
Old English sme(a)rcian, from a base shared by smile. The early sense was ‘to smile’; it later gained a notion of smugness or silliness.
wiktionary
From Middle English smirken, from Old English smercian, smearcian(“to smile, smirk”), corresponding to smerian + -cian (English -k), the former element from Proto-Germanic *smarōną(“to mock, scoff at”), and the latter from Proto-Germanic *-kōną. Compare Middle High German smielen/ smieren(“to smile”) ( > obsolete, rare German schmieren).
etymonline
smirk (v.)
Old English smearcian "to smile." No exact cognates in other languages, but probably related to smerian "to laugh at, scorn," from Proto-Germanic *smer-, *smar-, variant of PIE *smei- "to smile;" see smile (v.), which after c. 1500 gradually restricted smirk to the unpleasant sense "smile affectedly; grin in a malicious or smug way." In some 18c. glossaries smirk is still simply "to smile." Related: Smirked; smirking. The noun is recorded by 1560s.
smirk (n.)
1550s, from smirk (v.).
