One other thing just crossed my mind. Coughlan - Cough - Coughie or Coughey. How often have you hear someone referred to by just their surname (think about Downton Abbey's servants). When writing out Coughlan you can see where someone might shorten the name to Cough & then adding "ie" or "ey" to the name as a bit of whimsy. Coffee! Nicknames can stick for life.