A castrated male cat; also a hooked bolt or fastening device in machinery.
From Old French 'Gibert' (proper name), used generically to refer to tomcats similar to how 'John' became 'john' for toilet. The mechanical meaning is completely separate, possibly from 'giblet' or a person's name.
The word 'gib' for a neutered male cat is so old and forgotten that modern English speakers don't realize it's different from 'tom'—'tom' is intact and 'gib' is castrated, but we've collapsed these into just 'male cat.' Old specialized vocabulary disappears when it stops being necessary to distinguish the categories.
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