The two pieces in the title share similar forms. I want to know what the name for this form is, if there is one.
Basically, the form appears to be a repetition with an additional numbered fragment each time around, starting with one and going to 12.
Most people in English-speaking Western cultures know "The Twelve Days of Christmas," but if you don't know "Green Grow the Rushes-O" you can hear it here.
Songs like those are called cumulative songs (or perhaps songs of complexity since computer scientist Donald Knuth published this article).
I don't know of a term specifically for those based on the number twelve. Ten Green Bottles has only ten verses. It has numbers but it counts down rather than up and nothing gets added. The Barley Mow is a cumulative song but it has no numbers, and Oh Sir Jasper! actually drops a word each time through.
