I'd come across the explaination for the Peas Porridge Hot...origin. Here's what I got from:
http://www.vegparadise.com/highestperch52.html
If you were a young peasant child growing up in sixteenth century England, your frequent meals of pease porridge served hot, cold, and in-between may have prompted you to express your lack of enthusiasm in just such a verse.
A large kettle containing a thick porridge made of peas hung over the fire in many English and Scottish homes during the Middle Ages and was customary even in the sixteenth and seventeenth centuries. Because few of the peasants could afford meat, they based their meals on pease porridge with an abundance of whatever vegetables were on hand. When the fire died down at night, the morning porridge was quite cold. Each day the fire was relit, and more peas and vegetables were added to the kettle. Indeed, the original ingredients in the kettle could have been nine days old.