While they went doublin their mumper all the time

• doubling all the time → while they went doublin their mumper all the time
  • A first-draft version of Finnegans wake

• doubling → Vico's cyclic view of history, in which events repeat themselves → the New World's Dublin, Georgia, is a double of the Old World's Dublin, Ireland

• Dublin
  • A Finnegans Wake Gazetteer

• Doubling all the time: motto of Laurens Co, Georgia

• Doublin their mumper all the time - Being a mumper (a beggar) in Dublin, in reference to Giorgio, Joyce's son, who couldn't seem to become successful in life.