An expression of arrogance, meaning "I'm swingin' my dick in your face." It's origin is the code entry that generated a swingin' dick stick figure. In essence, a kind light-hearted way of just tellin' someone to fuck off. Also, a discreet way of doin' the same thing.
My boss was gettin' mouthy, so I said, 1-2-9 (one-two-nine), and went back to work with a smirk.