🔼The name Phlegon in the Bible
Since the Jesus-movement was illegal enough to have people fed to the lions in droves, it's unlikely that Paul was using the real names of actual Christians in Rome, but rather conveyed subliminal messages in a kind of literary code.
Note that the name Phlegon was highly unusual in the old world, and no other bearer of this name is known to us other than one of the four mythological horses that pulled Helios' chariot across the sky (see our article on ηλιος, helios, meaning sun). The other three were called Pyrois, Aeros and Aethon.
🔼Etymology of the name Phlegon
The name Phlegon comes from the verb φλεγω (phlego), meaning to burn brightly or shine like a fire:
For a meaning of the name Phlegon, Spiros Zodhiates (The Complete Wordstudy Dictionary) reads Flame and NOBSE Study Bible Name List has Scorching.