The protruding parts of the face below the mouth, or the plural of exercises where one pulls their body up to a bar.
From Old English 'cin' related to German 'Kinn', from Proto-Germanic. The exercise sense comes from the action of bringing the chin up to or over a horizontal bar, first recorded in early 1900s fitness contexts.
The chin is uniquely human - other primates have receding jawlines, but our prominent chins developed as our brains grew larger and our faces flattened. It's one of the few body parts that serves no clear survival purpose but became a symbol of determination and strength.
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