What does Taekju mean that he gave Zhenia his nickname???

i also didnt get it, if u somehow find the reason pls telll

bro im ab to read the novel now im scared ash omg (wish me luck)

Zhenya isn't the ML actual name. That's the name he told the MC to call him. So the Mc been calling him by a nickname. Zhenya is a nickname that is endearing or affectionate

TJ says that "I've been calling him my nickname" I don't know if it's a wrong translation. I'm taking it as Tj calling Zhenia "Zhenia" as he the one who gave him this name.