Portmanteau of monism + onanism.
In philosophy, monism is the view that a variety of things can be explained in terms of a single reality or substance, or a distinct source. Onism is a kind of monism, because your life is indeed limited to a single reality-by virtue of being restricted to a single body-but something is clearly missing.
Meanwhile, onanism is another word for masturbation, in which you find yourself temporarily transfixed inside your own menagerie of fantasies, like going on a sightseeing tour your own apartment-frustrating in its closed-off familiarity. Again, there's something missing.
Imagine how much more rich and satisfying it would be to have two bodies, not just one-so you could escape yourself for a while and live on either sides of the planet, or take a step back and see yourself whole, in full context with the rest of the world, with your face the right way around, your eyes unflattened, just as vivid as you appear to other people. It would be like those rapturous moments when one of your ears becomes unclogged and you can suddenly hear in stereo.
Everyone has one place that epitomises the exotic, which fills them with a kind of excitable dread. The most onistic place name I know is São Paulo. Maybe because it seems so sprawling and complicated, but without the open-armed iconography of Rio. Or maybe because it means Saint Paul, which is where I live. But instead of a tilde wandering over the word, we use a full stop, which is revealing. Anyway, it's almost like São Paulo is like a strange "bizarro hometown" on the other side of the world, a nexus of everything utterly unfamiliar that lingers somewhere below my feet.
You are here. You were lost at first, but soon began sketching yourself a map of the world-marking trails and boundaries, plotting the contours of your life.
And like the first explorers, sooner or later you have to contend with the blank spaces on the map. All the experiences you've never had. The part of you still aching to know what's out there, wondering what you're missing. Eventually these questions take on a weight of their own, and begin looming over your everyday life.
All the billions of doors you had to close in order to take a single step forward. All the things you haven't done and may never get around to doing; all the risks that may or may not have been real; all the destinations you didn't buy a ticket to; all the lights you see in the distance that you can only wonder about; all the alternate histories you narrowly avoided; all the fantasies that stay dormant inside your head; everything you're giving up, to be where you are right now; the questions that you wrongly assumed were unanswerable.
It's strange how little of the universe we actually get to see. Strange how many assumptions we have to make just to get by, stuck in only one body, in only one place at a time. Strange how many excuses we've invented to explain why so much of life belongs in the background. Strange that any of us could ever feel at home on such an alien world.
We sketch monsters on the map because we find their presence comforting. They guard the edges of the abyss, and force us to look away; so we can live comfortably in the Known World, at least for a little while.
But if someone were to ask you on your deathbed what it was like to live here on Earth, perhaps the only honest answer would be, "I don't know. I passed through it once, but I've never really been there."