Who Was Tertius / Tercius?

[Renicus Ferrarius]

I was watching Band of Brothers (episode 7, "The Breaking Point"), in which Lt. Ron Spiers and First Sergeant Lipton discuss Spiers's fearsome reputation. The following exchange takes place between them in a church, following the Battle of Foy:

Spiers: You wanna know if they're true or not. The stories about me? Did you ever notice with stories like that, everyone says they heard it from someone who was there. Then when you ask that person, they say *they* heard it from someone who was there. It's nothing new really. I bet if you went back two thousand years, you'd hear a couple centurions standing around yakking about how Tertius lopped off the heads of some Carthaginian prisoners.
Lipton: Well, maybe they kept talking about it because they never heard Tertius deny it.
Spiers: Maybe that's because Tertius knew there was some value to the men thinking he was the meanest, toughest son of a bitch in the whole Roman Legion.

After a while on google, I haven't been able to find anything concrete about a Roman soldier named Tertius (or Tercius; I'm not even sure of the spelling) who butchered a bunch of Carthaginian prisoners.

Was he a real soldier or was this just something they made up for the series? If they did make it up, it seems rather odd, given the number of real figures they could have used.

Any ideas?