Present participle of 'girn'; showing one's teeth in a grimace, or making a face.
From Scots 'girn' (to snarl or show teeth) plus '-ing' (Old English '-ung', forming present participles and gerunds). The gerund form allows 'girning' to function as a noun (the act of girning) or as a present participle.
Girning has become unexpectedly famous outside Scotland through British television shows and memes—there's even an annual 'World Gurning Championships' in Cumbria where contestants pull grotesque faces! The word went from obscure dialect term to internet culture, proving that language spreads through entertainment and humor as much as through traditional education.
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