Evolved (or devolved) from the phrase "Learn to play".
Often shortened even moreso to "l2p" or "L2P".
Frustrated Player: "That's not fair! Rogues can just pop out of vanish and stunlock me until I'm dead."
Rogue: "that's fine, lern2play."
Frustrated Player: "What the hell?! All you do is camp in the shadows and headshot me from far away!"
Sniper: "lol, lern2play n00b."