“Gotcha” — the collapsed form of “got you” — first appeared as a random pop-culture accouterment in the 1970s (a decade of random pop-culture accouterments). Merriam-Webster defines “gotcha” as “an unexpected usually disconcerting challenge, revelation or catch.” … The term is best delivered with a punch (or in all caps, with an exclamation point), suggesting some element of surprise, ambush or sudden twist. It packs a certain glib comic-book sensibility.
Then politicians adopted “gotcha” and (being politicians) promptly stripped it of its fun. It became a marker of grievance, umbrage and exasperation.
Mark Leibovich, “Out of Bounds”, The New York Times Magazine (10 May 2015), 13-14.