I have found an even more gory interpretation according to which “the meaning was about Bloody Mary torturing her victims. Silver bells stood for thumb screws that were torture devices, cockle shells that were a genital torture device, and the pretty maids in a row stood for the people lining up to be exeuted by the Halifax Gibbet. And the meaning of “How does your garden grow?” is said to refer to the cemetery, being that the more deaths, the more the cemetery “garden” would grow.”
In fact, with all its interpretations, the mystery behind which one is the true origin remains.
One thing is sure: this nursery rhyme as [almost] all others – and as the French comptines – has double meanings. Be it in the 16th century or the 18th century, during that time period and earlier, people had to preserve history any way they could. When the leaders of the country – any country and any leaders – wanted THEIR history to be the one to go down the ages, then the “opposition” used songs and poems. If writing was banned or if people were illiterate, ideas went on by way of oral tradition made easy by rhymes or music.
In the case of “Mary, Mary, quite contrary”, another version of political events – whichever they were – were kept, embedded in what would become Mother Goose nursery rhymes.
In “Au clair de la lune”, there is a libertine double entendre. But libertines were political opponents during the 17th century in France – and not the sexually depraved persons that a further distorted meaning made them in the following centuries. In Molière’s “Dom Juan”, the eponymous character is a libertine not because he mutiplies sexual intercourse with several women but because he believes that “deux et deux font quatre” (two plus two makes four): he is a rationalist and someone who does not believe in God and the religiously ordered world. The consequences were not only religious but temporal as well, and against the power that was: the king being king by God’s will, God being doubted or denied by Reason, there was no reason for the king’s power and authority. And the music of “Au clair de la lune” was composed by Lulli, the King Sun‘s composer. We are right in the reign of Louis XIV and the 17th century.
I wonder if something of the sinister meaning of “Mary, Mary, quite contrary” survived unconsciously in the minds of the listeners.
Part of Agatha Christie’s work is based on nursery rhymes: “One, Two, Buckle my Shoe”, the now-unpolitically correct “Ten Little Niggers” turned into “And They Were None”, “A Pocket Full of Rye”, “Five Little Pigs” among others. And among these others, a short story where Hercule Poirot is the detective: “How Does Your Garden Grow?”. This appeared in the short story collection entitled “Poirot’s Early Cases”, published in the UK in 1974.
Of course, Poirot’s first case was “The Mysterious Affair at Styles”, published much much earlier, in 1920. The 1974 collection was nicely giving a background to Hercule Poirot.
The short story “How Does Your Garden Grow?” cites the whole nursery ryhme that gives the solution of the enigma / the murder, and gives away the murderer / murderess. It was filmed for the Poirot’s miniseries in 1989, as one episode of the first seasons when they lasted but a little under an hour – no full films as later. This is an adaptation of the short story with some vagaries departing from the original, but quite faithful anyway.