Well Pat, I am really Penelope Gwynne, therefore the pg. The thom comes from my last name.
A little nurse story...when I worked in the hospital, the other team leader, Peggy and I usually shared the supervision of our floor. Our manager would usually call us by each other's names, so for years I would answer to either Peggy or Penny. We are both retired now, not sure if Peg still answers to my name!
And no, I never P. Green! Thanks for the laugh.