It's also the same basic melody that most people I know use for "Banks of the Sacramento"... so in answer to your question, yup. It is mos' definitely based off of a folksong. As a weird side note, pretty much anything you hear from pre-'60s warner cartoons that isn't instrumental is either a folk song or something from the pop culture of the period (and may have become a folksong since). Gotta love 'em!

M