Nursery rhyme
A nursery rhyme is a traditional song or poem taught to young children, originally in the nursery. Learning such verse assists in the development of vocabulary, and several examples deal with rudimentary counting skills. ("Eeny, meeny, miny, moe" is an example of a counting-out game.) In addition, specific actions, motions, or dances are often associated with particular songs.
Many cultures (though not all; see below) feature children's songs and verses that are passed down by oral tradition from one generation to the next (either from parent to child, or from older children to younger children). In the English language, the term "nursery rhyme" generally refers to those of European origin, and the best known examples are English and originated in or since the 17th century. Their origins were possibly a form of oral political cartoon, from an era when free speech could get the speaker imprisoned. Nursery rhymes, however, are often violent in nature, for example, in Jack and Jill, Jack fell down and "Broke his crown"- meaning breaking his skull.
Some nursery rhymes, however, are substantially older. "Sing a Song of Sixpence" exists in written records as far back as the Middle Ages. Arguably the most famous collection of nursery rhymes is that of Mother Goose. Some well known nursery rhymes originated in the United States, such as "Mary had a little lamb".
The nursery rhyme "Ring a Ring O'Roses" also known as "Ring Around The Rosie" is popularly believed to be a metaphorical reference to the Great Plague of London, although this has been widely discredited, particularly as none of the "symptoms" described by the poem even remotely correlate to those of the bubonic plague, and the first record of the rhyme's existence was not until 1881.
A credible interpretation of "Pop Goes the Weasel" is that it is about silk weavers taking their shuttle or bobbin (known as a "weasel"), to a pawnbrokers to obtain money for drinking. It is possible that the "eagle" mentioned in the song's third verse refers to The Eagle freehold pub along Shepherdess Walk in London, which was established as a music hall in 1825 and was rebuilt as a public house in 1901. This public house bears a plaque with this interpretation of the nursery rhyme and the pub's history. Shepherdhess Walk is just off the City Road mentioned in the same verse ("Up and down the City Road, in and out The Eagle"). Alternatively, the term "weasel" might be Cockney rhyming slang for a coat ("weasel and stoat" = "coat"), and the coat itself was pawned.
An amusing and ironic accidental hoax involving the rhyme "Sing a Song of Sixpence" was perpetrated on the Urban Legends Reference Pages.
Scholars occasionally think they have "all" nursery rhymes written down, or know the last time that a rhyme was in use (some fall out of favor). However, as nursery rhymes are mainly an oral tradition, nursery rhymes can surface anew (see Bill Bryson's book Made in America: An Informal History of the English Language in the United States for an excellent example).
There are some indigenous peoples which consider music sacred, so that only elder men may sing songs, and the songs are taught during sacred rituals in adulthood. It is forbidden for women or children to sing. Hence, these cultures do not have these kinds of songs.
Nursery rhyme revisionism
There has been some pressure, especially in the US and Canada, to make nursery rhymes (along with fairy tales and popular songs) "politically correct". Such bowdlerized versions may not perform the functions of catharsis for children, or allow them to imaginitively deal with violence and danger. Also, a society as a whole may be the poorer for it, because it loses opportunities to discuss obsolete values, even repulsive ones (like racism).