How did this guy found out my real name?

So i just entered in a game when suddenly a guy called me by my real name, i was like "wtf? how does this guy know my name?" well i asked him that, and he told me to search a name he gave me on facebook. i searched, i even went to my friend's page and nothing was there. I told him he wasn't on my friend list and asked him to explain how he got my real name. then he told me to let him win the match.

the real question here is: how the hell he got my real name?