(plural Tom Joneses)
The nearest synonyms (casanova, Don Juan, etc.) typically carry a connotation of actively seducing women. By contrast, a Tom Jones attracts women passively with his personal qualities, then gives in to the temptation to bed them.
After the title character in The History of Tom Jones, written by Henry Fielding and published in 1749; now perhaps also influenced by the Welsh singer of the same name and similar reputation.