Define I Could Tell You, But Then I'd Have To Kill You Meaning

I Could Tell You, But Then I'd Have To Kill You
a mob-like expression for the phrase "You will die if you hear my secret"

Guy 1: Duuuude, howdja get that Ipod touch?
Guy 2: i could tell you, but then i'd have to kill you
Guy 1: is that a no?
Guy 2: WTF was that supposed to mean?
Guy 1: you tell me,
Guy 2: NO!
By Merilee