"man of carnal adventures, connoisseur of seduction," 1888, from Giacomo Girolamo Casanova de Seignalt (1725-1798), the infamous debaucher. His name could be Englished as Jacob Jerome Newhouse, which is somewhat less romantic.
A ladies' man and seducer; lover-boy: Do ravish me, you wicked casanova you
[1880s+; fr the name of Giacomo Girolamo Casanova, 1725–98, a writer and legendary debaucher]