from wikipedia:
In April 1996, Buijs said in a Usenet posting, "As for the origin, I just made it up. I just kept running into the problem of what to call non-trans people in various discussions, and one day it just hit me: non-trans equals cis. Therefore, cisgendered."[6]
further:
The term has more recently been used in publications, such as a 2006 article in the Journal of Lesbian Studies[8] and Julia Serano's 2007 book Whipping Girl.[9] Serano also uses the related terms cissexual, which she defines as "people who are not transsexual and who have only ever experienced their subconscious and physical sexes as being aligned" (p. 12), and cissexism, "which is the belief that transsexuals' identified genders are inferior to, or less authentic than, those of cissexuals."[10]
so, basically, a made-up word to make sure that people who don't have issues with gender identity are defined as separate and non-empathetic to those who do.
edit: also, joking about something does not automatically mean one is implying that it is inferior, or less authentic than the so-called 'norm' one is using as a clarifier in the fucking joke.
Hey guess what? Somebody at some point "made-up" every single word we use in this whole fucking language.
As knowledge and understanding progress, so must language. Having a word for people who are not transgendered is necessary, because every other possible option diminishes trans people and genderqueer people as people whose gender identities are legitimate. We use words to define things, including the difference between people who ascribe to the gender assigned to them at birth and people who don't.
Do you think rape jokes are acceptable?
calm down, i just said that to piss you off anyway. but, it's still a pretty young word (coined on the internet), and a word that's appropriate in a clinical context isn't necessarily applicable to the rest of the world. i haven't heard a physician use it, for instance. and i damn sure didn't think that 'calling cisassination' or whatever it was was appropriate in the context of this thread. i found it offensive.
there are already words for people who are not transgendered. and, gender identities that are called into question by the owner of both the birth gender and their identifying gender, even if solidified by that same person, are still identities that have been called into question. legitimate or not is not the issue i actually take with your posts.
don't get me wrong. i am not in dispute of a transgender community nor am i faced with any problems with the issue itself. it's been, however, established that i have a problem with many aspects of activism, and while i am glad to see an emerging language and attempt at structuring the admittedly complicated aspects of gender identity and how it relates to the physical body, we just aren't there yet. getting there, but not there yet. and once 'we' get there, well, guess what. one still has to wait on society to dilute it into something they can understand, or at least feel some empathy for. otherwise, they're never going to accept.
frankly, i prefer the buck

approach to educating people about transgender issues. it's much simpler.
do i think rape jokes are acceptable? i make them, don't i? at a 'take back the night' gathering, probably not, no. but yes, i think almost any topic is acceptable as a joke
in the right context. nothing is intrinsically sacred, after all, and nothing exists in nature to define 'right' from 'wrong.' those are human concepts, and they derive from us thinking it isn't fair that we have to suffer and then die, much less watch others do same.