What does ding-a-derry mean?
Native speaker’s answer
Rebecca
"Ding-a-derry" is a made up phrase that the lyricist created in order for the song to flow well together and have a happy and memorable tune to it. In this context, it means something that is good and positive. When Scarecrow sings about how life will be ding-a-derry if he only had a brain, he means that life would be great and wonderful and better than it is now if he had a brain.