I haven't heard "Oh, Charlie is my darling" for years and definitely belongs to my childhood. At that time in the 1940's, it could often be heard on radio, generally sung in a classical manner by contraltos and certainly not as a folk song. Indeed I've never heard a Scotsman or Scotswoman of my acquaintance sing it.
When wanting to further my Scottish repertoire, I waded through Lieder, Songs und Gospels 1
coming up with this song as well as The World must be coming to an end
. The gay lilting tune is somewhat at odds with the implied seriousness of the lyrics.