
The big fight between Gertrude Stein and Hemingway was over the fact that she refused to call him "Papa", a name which he made up for himself. He would be known to ignore his best friends in a restaurant untill they addressed him with the correct self-appointed nom-de-guarre ! !
FYI
Other people that gave themselves their own nicknames:
Charlie "Yardbird " Parker
"Honest Abe" Lincoln
and
Mother "Old Corn Hole " Teresa