The Golden Age hero The Gay Ghost was the subject of a stealth retcon by DC Comics that attempted to not only alter his in-universe history, but rewrite his older issues as well. For a character debuting in 1942, the Gay Ghost had quite a dark origin story. Unfortunately, readers never took to the character and he only appeared sporadically at best, never ever receiving his own series. Still, DC saw fit to change a critical aspect of the Gay Ghost during reprints: his name.
The Gay Ghost first appeared in 1942's Sensation Comics #1. Killed by bandits while on his way to propose to the love of his life Deborah Wallace, 18th century Irish nobleman Keith Everet is granted powers by his ancestors to return to Earth - but only after Wallace returns to Ireland. Centuries later, Wallace's American descendent (also named Deborah Wallace) journeys to Ireland with her fiancé Charles Collins. Nazi spies attack Ireland, Charles is killed, and Keith subsequently possesses Charles' body to kill the Nazis and run away with Deborah Wallace to fight crime in America as the Gay Ghost.
The Gay Ghost had some problematic story elements - Keith infamously pretended to be Charles instead of reveal his true identity to Deborah Wallace, for one - but his name became dated within a decade as the colloquial meaning of the world "gay" changed. Creator Gardner Fox saw the writing on the wall and focused on other books such as the Justice Society of America. The Gay Ghost only appeared semi-regularly until 1945, but years later, reprints were ordered by DC (especially since Sensation Comics was an anthology series that featured Wonder Woman) - and arrived on shelves with a small change.
DC editorial had decided to rename Keith Everet's alter-ego to the Grim Ghost for all future appearances. Unfortunately, this change extended to the reprints as well. This retcon is akin to DC Comics reprinting old issues of Captain Marvel (back when he was owned by Fawcett) with his name changed to Shazam in a Golden-Age book. Language, however, is ever-changing; while DC attempted to modernize the Gay Ghost's name, the comics of the Silver Age were rife with colloquiums that modern audiences now find awkward. To cite a well-known example: the infamous Batman #66, published in 1951, centered around the Joker making a "boner": 1950s slang for an embarrassing mistake, error, or slip-up. Try as they might, no publisher can future-proof their comics, and trying only serves to muddy the water of comics history.
The Gay Ghost's last appearance was in Animal Man #25 in 1990. Since then, Keith Everet's presence hasn't graced a single issue. His dark origin would perhaps have worked better for a Bronze Age character than a colorful Golden Age hero, and his rewritten name actually hindered instead of helped his popularity (another hero called Grim Ghost was launched in 1975 and became popular enough to warrant a 2010 revival). The Gay Ghost is a footnote in comics history, but serves to showcase just how fast colloquialisms in language can develop.