A person who grimaces or makes facial expressions of pain or disapproval.
Grimace + -er (agent suffix). The -er suffix turns verbs into nouns meaning 'one who does the action.' First documented in the 1600s as people needed a word for chronic face-makers.
Medieval theater used specialized grimacers—performers whose job was literally just to make funny or gruesome faces for entertainment, a profession that seems hilariously specific by today's standards.
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