Transsexer: 2000, Transsexor: 1990 and Transsexism: 1977

Terminology by Cristan

First currently known derivations of the following terms…

Transsexer:

"Transsexer" - Queer Frontiers: Millennial Geographies, Genders, and Generations by Martin Meeker, 2000 (p 112)

Transsexor:

"Transsexor" - Homosexuality As Behavior and Identity: Dialogues of the Sexual Revolution By Lawrence Mass, 1990 (p 63)

Transsexism: 

"Transsexism" - Encyclopedia of Esoteric Man by Benjamin Walker, 1977 (p 27)