Plural of cad; men who behave dishonorably or disrespectfully, especially toward women; unscrupulous fellows.
From earlier cadet (younger son), from French cadet. The meaning shifted from a young gentleman to a rogue or dishonorable man in the 18th-19th centuries.
Victorian novels are filled with 'cads'—dishonorable men who betrayed women—and the word became so associated with bad behavior it almost lost its original military meaning!
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