Though celebrated in the both the East and the West, nothing is really known about Januarius. He is the patron of Naples (because he is buried there), blood banks, and volcanic eruptions - most likely because the reliquary which contains his blood liquefies and then seems to boil. Like so many, it looks like he was killed during the persecution of Diocletian. His name perhaps comes from the two-faced Roman god Janus, said to see forward and backwards, which might explain the boiling blood .
Perhaps also, his blood boiling may be a sign of not ire but passion. Perhaps he was "zealous for the Lord" like Elijah; perhaps he emulated Paul; we do not know - but we do know that his name is remembered, meaning that he lived for Christ in such a way that people who knew him remember also how he died for Christ.
Beloved, this saying is trustworthy:
whoever aspires to the office of bishop desires a noble task. Therefore, a bishop must be irreproachable, married only once, temperate, self-controlled, decent, hospitable, able to teach, not a drunkard, not aggressive, but gentle, not contentious, not a lover of money. He must manage his own household well, keeping his children under control with perfect dignity; for if a man does not know how to manage his own household, how can he take care of the Church of God? He should not be a recent convert, so that he may not become conceited and thus incur the Devil's punishment. He must also have a good reputation among outsiders, so that he may not fall into disgrace, the Devil's trap.
-- 1 Timothy 3:1-7