1350-1400;Middle Englishfrounen < Old Frenchfroignier, derivative of froigne surly expression, probably < Gaulish*frognā; compare Welshffroen,Old Bretonfron nostril, Old Irishsrón nose < Celtic*srognā or *sroknā
late 14c., from O.Fr. froignier "to frown or scowl, snort," related to frongne "scowling look," probably from Gaulish *frogna "nostril" (cf. Welsh ffroen "nose"), with a sense of "snort," or perhaps "haughty grimace." Related: Frowned; frowning.
The noun is from 1580s.