The phrase ("a penny for the ploughboy") is mentioned with some info HERE in an article on Plough Monday (January 7).

Today is Plough Monday in England. This is traditionally the first Monday after the Twelve Days of Christmas is over and represents getting back to work after the holidays.
On the Sunday before Plough Monday, ploughs are taken to church for a special blessing. On Plough Monday, however, you are supposed to decorate your plough and have your plough-boy (called a Plough Bullock or Plough Stot) drag your plough all over the neighborhood asking for "plough-money" ("a penny for the ploughboy") which is supposed to be spent in "a frolic," and food and drink. At the frolic, or banquet, later that day, the whole village joins in Mummers' plays, enacting ritual combat and symbolic death and revival, and Molly dancing. A queen, known as Bessy, is then crowned and farm workers do sword dances around the ploughs.
Incidentally, if someone fails to give money to the Plough Bullocks, they just take the plough and cut a big furrow right through the spoilsport's front lawn. What jolly fun! And you thought the British had a subtle sense of humor! Too bad the tradition didn't survive the journey to the New World.

~Masato