Many of the Roman gods weren’t exact clones of Greek gods, but they were more or less one to one matches. Zeus to the Greeks was now Jupiter to the Romans, Poseidon became Neptune, and Aphrodite was now Venus.
The Roman god Janus isn’t like this.
There isn’t a Greek counterpart to this god of portals who has two faces—one facing the future, and one facing the past. Janus’s control over portals extends to the more metaphorical realm, too, and the Romans thought of him as in charge of all types of transitions.
It is thanks to this attribute that the first month of the year is named. Janus oversaw the passage of one year to the next, so it made sense to call that transitional time Ianuarius, which became Januarius.
Janus looked both forward and backward at each year in transition, just as he always looked to both the past and to the present. He represented all kinds of duality.
It makes sense, then, that a few cunning linguists decided to call a certain category of words Janus words. Invoking the two-faced nature of the Roman god of portals and transitions made the meaning plain right away.
Still, they’re more properly (and commonly) called autoantonyms. If you already know that antonym means the opposite of a word, then maybe autoantonym can be just as effective as the term Janus word, but I really like the imagery.
Janus words include the word sanction, with which I have just the tiniest bit of practical experience. US Grappling needed to be sanctioned by the proper athletic commission if we were to legally run a jiu jitsu tournament in certain states, so we had to make sure to jump through the proper hoops. At the same time, if a similar organization did something wrong, they could end up being sanctioned.
You might dust a cake with powdered sugar, sprinkling tiny particles just as surely as I put baby powder in front of the fan when I was just old enough to stand up and reach over the edge. On the second face of that, you might want to do the exact opposite and pick up those tiny particles by dusting.
Did you seed the peppers by removing the seeds, or did you seed the garden by adding seeds? Did you leave something in a room, or did you leave that room? Are you weathering the storm, or are you being weathered by age?
Context is everything with Janus words, just as the Romans imagined it was for Janus himself. An omen might mean one thing to one interpretation, but another lens could provide a completely opposite prediction or advice.
This duality of language is itself a double-edged sword. On one hand, we really do have these autoantonyms in our language, and the person listening has to pay careful attention for context. On the other hand, the duality of meaning can be easily used by those seeking to make the truth unclear.
We are stuck with these words, though, so we might as well take the time to understand them!
It's just like when I recently trimmed too much hair off my head, but then I turned it around by using all that excess hair to trim my Christmas tree.
Sure, guests were understandably disturbed by seeing clumps of human hair hanging off tree branches, but at least I don't have to worry about having to socialize with people ever again.
The best-known example of Janus in popular culture is Janus Films, founded in 1956. This company is responsible for many North Americans' first exposure to the films of many of the great filmmakers of Italy, Sweden, Japan and other nations (it is currently affiliated with a modern equivalent, the Criterion Collection). And guess what they use for their logo?