Everyone's favorite First Order stormtrooper, lovingly dubbed TR-8R by meme-making fans, has an official designation now.
As suspected, TR-8R is in fact FN-2199, Lucasfilm confirmed on StarWars.com. The soldier was part of Finn's training squad, as detailed in Before the Awakening by Greg Rucka, a book released the same day as Star Wars: The Force Awakens. The book contains three novellas, one each giving a little backstory to Rey, Finn, and Poe Dameron.
Due to his designation, he's called "Nines" by his pals, and has red hair, as revealed in this Phil Noto art (the guy on the bench on the left). The character is part of an elite riot control squad, hence the electrified Z6 baton. Nines and Finn were paired with Zero and Slip during training. Slip was the stormtrooper killed at the start of the movie who streaked his own blood down Finn's helmet, very much a turning point for the hero.
The backstory explains why the call of "Traitor!" sounded quite so personal. It'll make fans look at Finn's face when he ignites that lightsaber and responds to Nines quite a bit more carefully in future viewings, too.
Lucasfilm teased that despite the shot from Chewbacca's almost impossibly powerful bowcaster blaster, there could be a rematch between Nines and Finn. "Let’s hope we haven’t seen the last of Nines. Or TR-8R. Who wouldn’t want to see Round 2…and all the memes it could inspire?" they say.
Even better, what if the next match is between Finn and Zero, the final two members of the squad?