An old English nursery rhyme. It is commonly thought to refer to the Black Death in the 17th century.
The English version of the rhyme is:
�Ring-a-ring-o-roses,
A pocketful of posies,
Atishoo! Atishoo!
They all fall down!�
The rhyme developed out of the fact that sneezing was the first sign that death by plague was imminent; those who sneezed died! The rhyme is rarely perceived to be as nasty as it really is; it�s about death!
However, Ian Munro's Ring A Ring A Roses FAQ at
http://www.ualberta.ca/~imunro/ring.html adds a few things. First, the rhyme's not old enough to be about the plague. Second, the early versions are clearly not about the plague.
The earliest printed source for the rhyme dates from 1881. A folklore book published in 1883 claims that versions of the rhyme were circulating in Massachusetts in 1790, but no printed evidence is available.
This earlier date is 125 years after the last major plague of the English-speaking world, and roughly 450 years after the Black Death, the 14th century plague most commonly associated with the poem.
Furthermore, as Ian's variations page demonstrates, most early versions of the rhyme would be extremely difficult to interpret as references to the plague.