Nursery Rhymes have been around for ages. Simple little children's songs, funny story rhymes, counting games all fall under this catagory. When fairy tales were relegated to the nursery they became lumped in with these rhymes. And indeed they do share many of the same characterstics.
The imagery associated with fairy tales, is also applied to nursery rhymes. The riddles that directly and indirectly influence and determine the tales are often classified as nursery rhymes.
"Under this category fall all the children's rhymes and songs, from counting games to historical rhymes.
One of the most famous images associated with these rhymes is Mother Goose, from the cover of a collection of rhymes written/collected by Charles Perrault.