In Roman mythology, the god with two faces looking backward and forward; now used to describe something that looks two ways or has a double nature.
From Latin 'Janus,' the Roman god of beginnings, endings, and transitions. The name possibly derives from 'ianus' (gateway), fitting since Janus guarded doorways. January is named after this god.
Janus is why we call the first month January—ancient Romans figured it made sense to start the year with a god looking both backward at the past year and forward to the coming one. The image of two faces is so powerful that 'two-faced' or 'two-faced person' entered English as a metaphor, though with a much meaner meaning!
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