In The Great Gatsby, why does Gatsby change his name? When did this occur?
"Jimmy" Gatz changes his name shortly after coming out of the military in order to make it sound more aristocratic and to hide is likely immigrant roots. Mainly, this change is directed toward impressing Daisy, whom he at this time is no longer courting as she decided to marry Tom while he was overseas fighting in the war.
Coming home a young retired Major, he fell into the illegal alcohol sales (bootlegging) business, as he had few marketable skills. He did not complete his university studies due to the war, and was working in a restaurant for a modest salary when Wolfenheimer found him and saw in him great potential.
It is truly sad that Gatz felt he had to change his entire identity just to impress a girl who, as fate had determined, would never see him as anything more than just a fling or person over which to make her cheating husband, Tom, jealous.