So when modern parents expose their kids to vintage nursery rhymes they’re engaging with a centuries-old tradition that, on the surface at least, is not only harmless, but potentially beneficial. But what about those twisted lyrics and dark back stories? To unpick the meanings behind the rhymes is to be thrust into a world not of sweet princesses and cute animals but of messy clerical politics, religious violence, sex, illness, murder, spies, traitors and the supernatural. A random sample of 10 popular nursery rhymes shows this.

The stuff of nightmares

Baa Baa Black Sheep is about the medieval wool tax, imposed in the 13th Century by King Edward I. Under the new rules, a third of the cost of a sack of wool went to him, another went to the church and the last to the farmer. (In the original version, nothing was therefore left for the little shepherd boy who lives down the lane). Black sheep were also considered bad luck because their fleeces, unable to be dyed, were less lucrative for the farmer.

Ring a Ring o Roses, or Ring Around the Rosie, may be about the 1665 Great Plague of London: the “rosie” being the malodorous rash that developed on the skin of bubonic plague sufferers, the stench of which then needed concealing with a “pocket full of posies”. The bubonic plague killed 15% of Britain’s population, hence “atishoo, atishoo, we all fall down (dead).”

Rock-a-bye Baby refers to events preceding the Glorious Revolution. The baby in question is supposed to be the son of King James II of England, but was widely believed to be another man’s child, smuggled into the birthing room to ensure a Roman Catholic heir. The rhyme is laced with connotation: the “wind” may be the Protestant forces blowing in from the Netherlands; the doomed “cradle” the royal House of Stuart. The earliest recorded version of the words in print contained the ominous footnote: “This may serve as a warning to the Proud and Ambitious, who climb so high that they generally fall at last”.

Mary, Mary Quite Contrary may be about Bloody Mary, daughter of King Henry VIII and concerns the torture and murder of Protestants. Queen Mary was a staunch Catholic and her “garden” here is an allusion to the graveyards which were filling with Protestant martyrs. The “silver bells” were thumbscrews; while “cockleshells” are believed to be instruments of torture which were attached to male genitals.

Goosey Goosey Gander is another tale of religious persecution but from the other side: it reflects a time when Catholic priests would have to say their forbidden Latin-based prayers in secret – even in the privacy of their own home.

Ladybird, Ladybird is also about 16th Century Catholics in Protestant England and the priests who were burned at the stake for their beliefs.

Lucy Locket is about a famous spat between two legendary 18th Century prostitutes.

Here We Go Round the Mulberry Bush originated, according to historian RS Duncan, at Wakefield Prison in England, where female inmates had to exercise around a mulberry tree in the prison yard.

Oranges and Lemons follows a condemned man en route to his execution – “Here comes a chopper / To chop off your head!” – past a slew of famous London churches: St Clemens, St Martins, Old Bailey, Bow, Stepney, and Shoreditch.