Webster's defines "namesake" as "one who is named after another or for whom another is named." For instance, anyone with Jr. in his name is a namesake of his father.
Ashoke and Ashima Ganguli, who emigrate to America from India, name their son Gogol in honor of the Russian writer Nikolai Gogol. When he was younger, Ashoke survived a train wreck, and the only thing he was able to salvage from his belongings was a tattered copy of Gogol's novel The Overcoat. Ashoke wasn't necessarily a huge fan of Gogol. They couldn't take the baby home from the hospital without a name, and Gogol was the first one that popped into Ashoke's head.
Therefore, the namesake of the title is Gogol Ganguli. The novel centers around his search for self as a first-generation American with a strange Russian name.
namesake means "one who shares the name of another person".
in the book, the namesake Gogol is the namesake of Nikolai Gogol who is a famous Russian author. But the irony in the book is Nikolai is the favourite author of Ashoke and its a reason why he named his son as Gogol, and the son dislikes his name.
the whole novel revols around the name of the protagonist, Gogol.this is probably the reason why the book is named as the namesake.