"The Medill girl would marry him and she wouldn't marry him. She was having such a good time that she hated to take such a definite step. Meanwhile, their secret engagement had got so long that it seemed as if any day it might break off of its own weight. A little man named Warburton who knew it all, persuaded Perry to superman her, to get marriage license and go up to the Medill house and tell her she'd have to marry him at once or call it off forever..."
From my brief internet search, I discovered Superman first appeared in 1932. (You can read more about Superman at Wikipedia.) So I was able to rule out the Comic Superman reference, which I was pretty sure it was not.
I then was lead to the term Ubermensch coined by Nietzsche in 1883. Ubermensch is sometimes translated as superman or over man, which seems to have a larger more philosophical meaning than how Fitzgerald used the term in the Camels Back ( Ubermensch -wiki)
I was then lead to the George Bernard Shaw 1903 stage play- Man and Superman. And from what I can tell this is the reference Fitzgerald was using, where one of Shaw's characters persistently tries to get another to marry them.
Cliff's notes reading the summary and even that caused me to wander. I am blaming it on the weather being far to nice to think too deeply.
Anyways, if anyone knows what Fitzgerald meant by "superman her", I would appreciate the insight.
Read Man and Superman Online