(Ah, the Apple Trees) When the World Was Young is a popular song composed by M. Philippe-Gerard, with lyrics by Angele Vannier. The English lyrics were written by Johnny Mercer. The original French title was "Le Chevalier de Paris".
English lyrics were originally written by Carl Sigman, but these were rejected by the music publisher, Mickey Goldsen. Sigman suggested Mercer, and Mercer wrote the English lyrics (three verses and three choruses) in three days. [1]
The song is from the perspective of an aging Parisian "boulevardier"/"couquette", as s/he reviews their life.