Merriam-Webster's Collegiate® Dictionary, 11th Edition
FROWN
I. verb
Etymology: Middle English frounen, from Middle French frogner to snort, frown, of Celtic origin; akin to Welsh ffroen nostril, Old Irish srón nose
Date: 14th century
intransitive verb to contract the brow in displeasure or concentration, to give evidence of displeasure or disapproval by or as if by facial expression , transitive verb to show displeasure with or disapproval of especially by facial expression, frowner noun frowningly adverb
II. noun
Date: 1581
an expression of displeasure, a wrinkling of the brow in displeasure or concentration