Where does the 丸 in boys' names come from?

I'd noticed that 丸 is attached to some boys' names, or boy animals, or manly object, especially in folklore. I just assumed it was a marker to indicate boydom or something. However, while watching 世界のみんなに聞いてみた today, I learned that the 丸 apparently comes from お丸. Let me paste the definition of お丸 from gogen-allguide.com below for you:

おまるとは、幼児や病人が用いる、持ち運びのできる便器。

 Yes. The　丸 comes from a Japanese word for bedpan or chamber pot. Why on earth would you attach that to your child's name?  Or a really cool sword? Or a beloved dog?

The custom didn't stem from angry parents who bitterly called their babies "Stinky Poo Pot" though. It seems that the act of adding 丸 to your child's name kept him safe from monsters, who apparently, like humans, curl their lips in disgust and turn tail at the thought of chamber pots and the contents within. Not a bad strategy.