In baseball, a hit ball that travels along the ground, or a punishment where someone is confined to home.
From 'ground' + the agent suffix '-er.' In baseball, the term became standard in the 19th century. The punishment meaning developed in 20th-century American English.
The baseball term 'grounder' is so common that Americans extended it to mean any punishment involving being stuck at home—the sports slang became parenting vocabulary!
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