Some grow up from rhymes based around historical events - 'Ringa Ringa Roses' is a prime example - "Ringa ringa roses, a pocket full of posies, atishoo atishoo we all fall down!" is derived from symptoms of The Plague - the 'roses' refer to the red blotchy rash that sufferers developed, 'posies' were the bunches of dried flowers people carried in the belief that it kept The Plague away, the 'atishoo' is sneezing, believed to be another symptom, and 'we all fall down' is the inevitable death from the disease. A children's rhyme based in more sinister historical beliefs from the time.