Until very recently, the prefixes “cis” and “trans” were mostly used as terms of art in geography. The most common usage was Cisalpine and Transalpine Gaul (or Europe). The former meant “on this side” of the Alps (from the viewpoint of Rome), the later “on the other side.” Transylvania is another very well-known geographical construction of this sort; it means, of course, the land “beyond the woods.”
These are by no means the only examples, for geographers long found these locutions very handy (and then they shifted their attention from the regions of the earth to the horrors of “whiteness”). Far west Texas can be called, for instance, the Transpecos.
It is useful to keep these geographical expressions in mind when trying to understand the recent constructions “transsexual” and “cisgender.” If we take the geographic metaphor seriously (as we should), these words do not denote a relation to one or the other sex, but to dimorphic sexuality generally. A “transsexual” is not just someone who has “transitioned” to the other sex, but rather someone who has “gone beyond,” or “to the other side of,” traditional sexuality. To be “cisgender” is to remain within, or “on this side of,” this boundary.
This would parallel the true meaning of the word “transnational,” which does not denote a company with international operations, but rather a company that has moved “beyond” the categories of nation and national identity.
It may help to imagine this boundary of sexuality as a mountain range like the Alps, with “cisgender humanity” holding steadfast on the south side, in a sexual analogue of the Plains of Lombardy, and “transsexual” humanity having crossed over the mountains into sexual Savoy.
Those who are today described as “curious” or “questioning” are, in this analogy, stumbling around in the Passes of St. Gotthard or St. Bernard. Perhaps a large dog will bring them a keg of brandy if they fall into a snowdrift!
With this image in mind, we can see that men and women who have undergone “gender reassignment” are only a small part of the true “transsexual” population. Indeed, some men who live as women, but are in all other respects resolutely cisgender in outlook, might properly be regarded as a curious clan living rather high up the slope on this side of the sexual mountains. The transsexuals are those who have crossed the mountains and moved “beyond” traditional sexual categories, whether or not they have lost their genitals along the way. Advocates of absolute sexual equality strike me as transsexuals, for instance.
To be transsexual is, in other words, to be on the side of the sexual revolution. To be cisgender is to be a sexual counterrevolutionary. This seems to be the way transsexuals actually understand the words when they impugn us as “cisgender pigs,” and I think we would be better off if this were the way we understood the words as well.
Before the great tunnels were bored through the Alps, making it virtually effortless to move from cis to trans, crossing over the mountains was difficult and dangerous. As noted above, the most common routes were the Passes of St. Gotthard and St. Bernard. Descending from St. Gotthard’s Pass into Transalpine Europe, the pilgrim came to the famous Devil’s Bridge. It was when he had crossed this bridge that he was truly “on the other side.”