 Dictionaries also differ with regard to the preferred spelling of the disorder with the "Collins English Dictionary – Complete and Unabridged" using the hyphenated spelling, and the "American Heritage Dictionary of the English Language, Fifth Edition" and the "Random House Kernerman Webster's College Dictionary" giving the non-hyphenated spelling.Some at the Pentagon have used the terminology "PTSS" (syndrome instead of disorder, to avoid connotation of stigma), or just "PTS".The comedian George Carlin criticized the euphemism treadmill which led to progressive change of the way PTSD was referred to over the course of the 20th century, from "shell shock" in the First World War to the "battle fatigue" in the Second World War, to "operational exhaustion" in the Korean War, to the current "post-traumatic stress disorder", coined during the Vietnam War, which "added a hyphen" and which, he commented, "completely burie[s] [the pain] under jargon".