黄美姬的回答：

Merry go round, getting on the ride is fun and makes kids happy, another word for happy is merry especially in the old days. The ride goes around and around so a perfect name would be "merry go round". --From WebAnswers

守望&幸福的回答：

来源于一儿歌 http://www.bl61.cn/book/b/31983.html