yeah, it’s not that old - it’s more like a term that became taboo as queer activism attempted to develop more inclusive language, starting with transgender which was meant to extend beyond transsexuals to include cross-dressers, drag performers, etc. … unfortunately people just started using “transgender” to mean “transsexual”, so then there was “trans*” as the new umbrella term, and then finally “trans”.

Every step along the way I think what happens is that the umbrella term just becomes the new way to refer to the default, mainstream conception of a trans person, which is basically a transsexual - a person who socially and medically transitions from one binary sex to another binary sex.

Probably what most made people abandon “transsexual” as a term was the way the term was adopted by truscum (trans people who don’t believe in non-binary people and who gatekeep trans identity mostly through pseudo-science and junk science).