frownyoudaoicibaDictYouDict
frown: [14] Probably the underlying notion of frowning is ‘snorting’ rather than ‘wrinkling the brows’. It comes from Old French froignier, which meant ‘snort’ as well as ‘frown’. It is assumed to have been adopted into French from a Celtic language of Gaul, and would therefore have been related to Welsh ffroen ‘nostril’.
frown (v.)youdaoicibaDictYouDict
"contract the brows as an expression of displeasure," late 14c., from Old French frognier "to frown or scowl, snort, turn up one's nose" (preserved in Modern French refrogner), related to froigne "scowling look," probably from Gaulish *frogna "nostril" (compare Welsh ffroen "nose"), with a sense of "snort," or perhaps "haughty grimace." Figurative transitive sense "look with displeasure" is from 1570s. Related: Frowned; frowning.
frown (n.)youdaoicibaDictYouDict
1580s, from frown (v.).