I don't normally recommend listening to George Carlin to anyone, but he did a whole routine on how different names for the same thing evolved. In WWI, it was called 'shell shocked'; in WWII, it was called 'battle fatigue' then in Viet Nam, it was PTSD (Actually, back then, it was post traumatic stress syndrome. Not sure when they changed it from a syndrome to a disorder.)
If you want to hear it, you can look it up on YouTube yourself; I'm not going to post a link here.