As a result of popular culture (as much as anything else), most people are now aware of the meaning of trans (or transgender).
It refers to someone who was assigned a gender at birth but who later takes steps to affirm another gender that more closely aligns with their true identity.
The trans part is derived from Latin and means ‘across’ or ‘on the other side’. We see it in words that involve crossing boundaries, barriers and other things: transatlantic, transgression, transition, translation …
A bit less familiar is the expression cis, now used to refer to people who were assigned a gender at birth that they remain OK with. For example: Cis white men make up the majority of partners at law firms.
Cis is the Latin opposite of trans, and means ‘this side of’.
So Cisalpine Gaul was the part of the province on the Roman side of the Alps; to get to Transalpine Gaul, the Romans had to cross the mountains. (The Gauls would have seen things differently, of course).
In the early twentieth century, Cisjordan and Transjordan were used to describe the territories on either side of the River Jordan. The former is now more usually called the West Bank, although the French still refer to it as Cisjordanie. The early twentieth-century Emirate of Transjordan became the modern Kingdom of Jordan.
Those who really know their history will recognise Cisleithania as a name for the non-Hungarian parts of the Austro-Hungarian Empire, the Leitha being a small tributary of the Danube that marks the historical border between the Archduchy of Austria and the Kingdom of Hungary.
Note that in all the geographic senses, the definition of what is on this side and what is across the way is determined by the perspective of the more powerful group.
I suspect trans people might say the same thing.