"Geminus" is the first epithet in Macrobius's list. Although the etymology of the word is unclear, it is certainly related to his most typical character, that of having two faces or heads. The proof are the numerous equivalent expressions. The origin of this epithet might be either concrete, referring directly to the image of the god reproduced on coins and supposed to have been introduced by king Numa in the sanctuary at the lowest point of the Argiletum, or to a feature of the Ianus of the "Porta Belli", the double gate ritually opened at the beginning of wars, or abstract, deriving metaphorically from the liminal, intermediary functions of the god themselves: both in time and space passages connected two different spheres, realms or worlds. The "Janus quadrifrons" or "quadriformis", brought according to tradition from Falerii in 241 BC and installed by Domitian in the Forum Transitorium, although having a different meaning, seems to be connected to the same theological complex, as its image purports an ability to rule over every direction, element and time of the year. It did not give rise to a new epithet though.