Famously sung by Elvis Presley, the melody is actually based on " Plaisir d'amour ", a popular French love song composed in 1784 by Jean-Paul-Égide Martini. The song was initially written from the perspective of a woman as "Can't Help Falling in Love with Him"
WARNING:  Clicking the "Plaisir d'amour" text link in the song information will take you to a page with fast FLASHING images.