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1809, from Tom + cat; probably influenced by Tom the Cat in the popular children's book "The Life and Adventures of a Cat" (1760); replaced earlier Gib-cat, from diminutive of Gilbert, though Tom was applied to male kittens c.1300. Used of the males of other beasts and birds since 1791. Cf. also Tibert. The verb meaning "to pursue women promiscuously for sexual gratification" is recorded from 1927.
: In his younger days he was a notorious tomcatverb
To pursue male sexual activity avidly
[1927+; fr the common name for a male cat, popularized by the 1760 book The Life and Adventures of a Cat, in which the creature was named Tom]