In this case the language appropriated is "trans/transgender". Notice how you rarely hear the terms transsexual or transvestite anymore. That's because the movement has been co-opted by the transvestites, obscuring that by making out the two are the same under the umbrella of transgender.

There's actually some pretty interesting reading that illustrates pretty well how we ended up in this mess. Basically the modern trans movement as we know it today can be traced back to Virginia Prince, the publisher of Transvestia magazine, Virginia openly admitted that his first experience wearing women's clothes involved feeling aroused at wearing his mother's underwear (what a surprise). Prince later went onto found Full Personality Expression, arguing that suppressing transvestism was denying a part of the personality, which later became the Society for the Second Self. The UK branch of Tri-Ess (I'm guessing they used that as their shorthand so it wasn't SSS) would be called the Beaumont Society. Both of these organisations on both sides of the pond were for straight crossdressers and the Beaumont Society even had men sign a declaration swearing they weren't gay, they couldn't afford to be seen to be affiliated with those dirty homos, you see. Members of the Beaumont Society as well as Professor Stephen Whittle a transman would later go onto found Press for Change, an organisation who were highly influential in pushing Stonewall into the situation they currently find themselves in.