Originally, the title of [Fitzgerald's novel] was “Trimalchio,” based on an ancient satire of a man called Trimalchio who dresses up to be rich.
The idea behind Trimalchio and Gatsby is a similar one. Each of these characters poses as something he is not - rich. Though Gatsby does achieve/acquire wealth, he remains a poseur, playing a role and presenting himself under false pretenses.
Gatsby is not the person he says he is in terms of the personal history he presents in public and to Nick, initially. Gatsby is not even "Gatsby" fundamentally. He is Jay Gatz.
Presenting himself as Jay Gatsby, Gatsby has taken on a part akin to the ancient story of Trimalchio. As a relative of the figure of the roman satire, Gatsby also serves to explore and expose some of the false values of the rich, their immorality, haughtiness and recklessness pride.
Some of the power of Fitzgerald's narrative comes from this allusion to the roman satire. Gatsby is not "just a man" or just a character. In addition to being a developed character in the novel, he is a representative of a type.
Trimalchio is a character in the Satyricon by Petronius, written in the first century AD. The character is a freed slave who becomes rich through devious means. Chapter 7 of The Great Gatsby begins,
"It was when curiosity about Gatsby was at its highest that the lights in his house failed to go on one Saturday night—and, as obscurely as it had begun, his career as Trimalchio was over."
After Gatsby reunites with Daisy, Gatsby does not have the raucous parties he used to have. Therefore, he is no longer a Trimalchio-like figure, and he is no longer trying to prove his worth to the world by giving parties design to attract Daisy. Fitzgerald considered naming his book Trimalchio or Trimalchio in West Egg, as Gatsby, who is from humble origins, is similar to this slave in Roman literature. Trimalchio has become a symbol of characters in literature who emerge from humble origins and who try to overcome these origins by leading a lavish lifestyle.
Trimalchio is a character in the Roman novel, The Satyricon by Petronius. He is a freedman who through hard work and perseverance attained power and wealth. He relates to Gatsby because both of them weren't born rich and both got their wealth through perseverance and they both throw lavish parties.