Janus should have been Roman; interestingly, looks like Hecate is the Greek counterpart -- if one goes by Wikipedia's suggestion, anyway.
*Insert hundreds of Chrono fanfics about a parallel universe where Schala gets a little sis named "Hecate" in a parallel universe.*
Hmm, I'm not sure whether the Compendium ever had the name origin in the wiki entry. I wonder if this might have been in one of the early editorials, though.