How do we learn nursery rhymes?

I do not remember being taught nursery rhymes, either by my mother or in kindergarten, but off the top of my head I can think of at least a dozen of them. I correctly sense that they have been around for hundreds of years. Do you specifically remember being taught them? Do those of you under twenty know nursery rhymes? If I say Jack and Jill or Three Blind Mice, does this mean anything to you?

For anyone interested, here is a Web site that gives origins of nursery rhymes, some of which are a bit gruesome.