Mary Mary quite contrary,
How does your garden grow?
With silver bells and cockleshells
And pretty maids all in a row.
We Thought it Meant...
A cute old woman with an interest in horticulture.
But Some Experts Say...
Queen "Bloody" Mary was popular enough to frequent a number of nursery rhymes, which is pretty impressive all these centuries later.
Anyway, in this delightful tune, Mary is addressed first-hand about all of the poor saps she's sent to the graveyard (her garden). The silver bells refer to instruments of torture that crushed the thumb with the tightening of a screw, and cockleshells (heh) were torture devices that were attached to the genitals. Come on, don't act surprised. They're called cockleshells...
The maids in the final line allude to the newly invented guillotine, which was nicknamed The Maiden.
taken from cracked.com