Showing courage and determination, especially in doing something difficult or dangerous.
From 'guts' (intestines, but also used for courage) plus -y. The phrase 'have the guts to do something' dates to the 1800s, as intestines were metaphorically associated with courage and strength.
Many languages connect bravery to internal organs—Spanish uses 'agallas' (gills), Japanese uses 'kimo' (liver), and English uses 'guts'—suggesting that ancient humans felt courage as a physical sensation in their belly.
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