Of course the only question people ever ask about this long forgotten player nowadays is, "How did he get the nickname Peggy?"
I do not know the answer in full certainty, but it appears that "Peggy O'Neill" was a very popular song in the 1920s, especially in New England. Perhaps the name stuck from there.
O'Neill the hockey player (also listed as O'Neil by some sources) did not score very often. In those 156 games he had just 6 goals plus 30 assists. And he was a forward, not a defenseman!