"I met an old man who wouldn't say his prayers, I took him by the left leg and threw him down the stairs."

I heard these lines this week on the radio.  A quick search revealed that they come from the nursery rhyme "Goosey Goosey Gander":

Goosey Goosey Gander where shall I wander,
Upstairs, downstairs and in my lady's chamber.
There I met an old man who wouldn't say his prayers,
I took him by the left leg and threw him down the stairs. 

Here's one explanation for this curious verse:

"I read that it referred to the post Civil War period (middle 17th century) and Cromwell's soldiers who marched in "goose-step", which gives the title and first line. Also, the version of the rhyme I heard had the third line as, "There I met an old man a-saying of his prayers". This referred to (as you mention) a Catholic, possibly a Priest, praying and the line: "I took him by the left leg and threw him down the stairs" alluded to the nickname "left-footer", that a Catholic is sometimes called in Britain. The overall meaning was that the Roundhead soldiers were searching out Catholics, particularly Priests, hiding in the houses of friends, and when found they were ill-treated".