He only has one line in The Force Awakens, but it’s a good one.
Affectionately dubbed “TR-8R” by the fans in reference to his catch (only) phrase, the film didn’t tell us a whole lot about this stormtrooper, or why he was so good at spinning things. This being the Star Wars universe though, you just know he has an elaborate backstory.
There’s a canon novel out right now called Before the Awakening, which provides a brief glimpse at the lives of Finn, Rey, and Poe before the events of TFA. Finn’s story is particularly revealing, detailing the training process of First Order troopers.
We learn that before defecting, Finn was part of a four-man fireteam composed of himself (FN-2187), FN-2199, FN-2000, and FN-2003. They were nicknamed Nines, Zero, and Slip respectively. The first two got their nicknames from their numbered designations, while Slip got his because he was the screw-up of the group, and was always slipping up.
Finn meanwhile did not get a nickname, despite becoming the squad leader. Why? Another stormtrooper explains it, calling Finn, “An outsider. You’re on the outside, and you’ll always be looking in and wondering why you don’t belong.”
Outside of that “dangerous level of empathy” for his squadmates though, as Captain Phasma describes it, Finn was a model trooper. He scored in the top 1% of his class, and was being fast tracked for officer’s training. That is, before he stole a TIE Fighter of course.
We never find out what happened to FN-2003, but as for Slip, well, he was that stormtrooper who was killed in the opening of TFA (confirmed in the visual dictionary). Poor guy.
And if you haven’t guessed it already, yup, FN-2199 (AKA “Nines”) was the stormtrooper who confronted Finn on Takodana. He’s the one seated in the back with the red hair in the image below:
As for those sick spin skills, there’s a story behind that as well. After training, Nines became part of the First Order’s Riot Control unit, an elite squad trained for dealing with crime and uprisings. Members of that squad carry non-lethal weapons (betaplast shields and Z6 batons), although obviously that baton can be pretty deadly if used right.
So with Nines and Slip both dead, I wonder if Zero will make an appearance next. My guess would be yes, quite possibly in a novel or comic book story set before or around TFA.