Cisgender and it's Ancient Roman Latin prefix cis (translates to "on the same side of" and is the opposite of the prefix trans) are not offensive regardless what Elon Musk or JK Rowling say. They're in dictionaries, feel free to look them up.
Slightly OT but as an autistic linguistics obsessed pedant, I'm really tired of TRAs claiming this.
'Cis' barely exists in Classical Latin and where it does it is used overwhelmingly for geographical locations eg Cisalpine Gaul, Transalpine Gaul.
However it would be far more common in Latin to use the ablative or the older locative, which eventually got subsumed into the ablative.
TRAs make these ahistorical claims, in my view, because they want to give the impression that trans people have always existed, even as far back as Ancient Rome guys!
In actual fact this is bollocks. A rarely used locative prefix is not the same as the idea that people can have souls which are gendered differently than their bodies, which there is zero evidence the Romans believed, and plenty of evidence they did not, as they were a strikingly practical people.