Name of the month January comes from the Roman god Janus. The Latin name of the month of January is Ianuarius. He was the god of all origins, and also the guardian of doors, gates, passages and bridges, the patron of alliances and agreements. His main celebration was the first day of the year (calendae Ianuariae), when people made each other wishes and gave small gifts (such as a baked cake called ianual) for a good omen; at that time, newly elected officials were also appointed.
The houses were decorated with wreaths and laurel branches. On another public holiday, called Agonium, celebrated on January 9, a priest replacing the ruler (rex sacrorumrex sacrorum) offered Janus a ram. In addition, Janus was also devoted to every first day of the month in which he received a sacrifice of wine, incense and fruit. Janus was a purely Roman god with no equivalent in Greek mythology, and practicing his cult was not found outside of Rome.
Traditionally, he was depicted as a serious male figure with two bearded faces, one of which was looking east, the other west. Since he was a god who was looking, both backwards and forwards, the choice of his name for the name of the first month of the year seems to be understandable.