I doubt if anyone seriously thought that the song originated in 1939

I'm going to have to look at some of those there books before I ask any more stupid questions.

In half-hearted defence of the original question, the oldest date that's attached to a song called "Pleasant & Delightful", catalogued online, is the Digitrad's 1963. (That title doesn't appear in the YG, the Folkinfo db or the Coppers' collection; Cantaria has it but dates it back to 1970(!).) Obviously, what this tells me is a) not to rely on online catalogues & b) not to rely on titles staying the same.