I thought the word "retcon" was created to specifically describe how Doctor Who would loosely change past continuity series to series and season to season.
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I believe the word originated with comic books, with reference to later writers and artists going back to tweak a character's origin or continuity, with the changes then assumed to have always been in place. I remember it being used in Marvel Comics letter pages back in the seventies.
As in "Tony Stark was originally injured in Viet Nam, but that's been retconned so that now he was injured in the Middle East instead."
None of this stuff is set in stone.