The very term "comic book". Unless you think Batman is hilarious. Whichhe is, but still....
The 'DC' in DC Comics originally stood for Detective Comics. Very few of their comics today feature actual detectives, and officially the acronym no longer has any meaning.note If it did, the company's name would be "Detective Comics Comics." Similarly, while the actual Detective Comics publication does feature Batman, "the world's greatest detective", many of the stories therein feature little or no actual detective work.
Similarly, Action Comics was intended to be an anthology title of, well, action comics. The debut of Superman in the first issue and his subsequent popularity led to the character taking over the line.
While Cable & Deadpool always had the tendency to focus more on the latter than the former, the title became obsolete once Cable (temporarily) died. They lampshaded this by crossing out the word "Cable" on the covers and replacing it with the name of the guest stars.
From #3 onwards of the comic series Nextwave, its official title was "Nextwave: Agents of H.A.T.E" (due to trademark issues). This was despite the fact they stopped being agents of H.A.T.E by the end of #1, giving it an Artifact Title from the beginning. This was lampshaded in every comics recap after it became irrelevant.
The "Stories" in Walt Disney's Comics and Stories were originally passages of text with minimal illustrations (and thus, "stories" about Disney characters) rather than actual comic strips. As those faded out of use in favour for comics, the official title of the series remained Walt Disney's Comics and Stories, but the title logo simply reads Walt Disney's Comics.
When Donald Duck's superhero alter-ego from the Italian comics, originally known as Paperinik, made its way into American comics in Disney Adventures, the characters was given the English name of the Duck Avenger, the obvious reason for the change being so that he'd have the same initials as the magazine. Nine years later, the Duck Avenger is still the character's official English name, even though Disney Adventures is no longer published.
In Vol. 4 of Mirage's Teenage Mutant Ninja Turtles series, the turtles are now in their thirties, having aged in real time since the original series.
2000AD's title was chosen in 1977 because it sounded futuristic. Publishers IPC Media didn't really think about this trope when they okayed it. They launched new titles on a regular basis, and the predicted lifespan of a children's title (as it was originally) was 18 months. In the 1990s there were a few attempts to change the name to something less "dated", all of which were roundly rejected by the fans. It's still called 2000 AD today. It's now more of a Badass Boast since the stance in Prog 2000 (the last issue released in 1999)note Since 1999, the prog that covers the Christmas / New Year period used the new year as the issue number, as of mid-late 2012 the regular weekly issues are "only" up to the early 1800s said "We were here first. The year can change its name."
None of the main characters in Knights of the Old Republic are (Jedi) Knights: Zayne is a Padawan who missed his first opportunity due to a combination of circumstances and later refused the offer of knighthood after clearing his name, and his companions never had any formal Jedi training (and most of them aren't even Force-sensitive). The comic inherited that title from the video game, which in turn got it from an even earlier arc of the Tales of the Jedi limited comic series.
When Jack Kirby and Joe Simon created the Newsboy Legion in The Golden Age of Comic Books, they were so-called because they were orphans who sold newspapers to earn a living. This had become an anachronism in later years, which was addressed in several different ways:
When Kirby introduced their identical sons in the Bronze Age, they were also known as the Newsboy Legion, even though they'd never sold a paper in their lives.
The current incarnation of the Legion are clones of the originals (the sons don't exist Post Crisis), and they still don't sell papers.
Walter Simonson tried to bring them up-to-date in Orion as the Newsgroup Legion, a term more recently used by Jimmy Olsen (although it remains to be seen if he's talking about the same kids).
The home titles of DC Comics' Enemy Ace feature were Our Army At War and Star-Spangled War Stories. For the mostly-American readership, the tales of German World War One ace Hans von Hammer were neither "star-spangled" nor about "our" army.
Stephanie Brown, Batgirl 2009, originally operated under the superhero identity of 'the Spoiler.' Her name and modus operandi came from her relationship with her father, the Cluemaster, who was a B-grade Riddler knockoff. Stephanie grew to despise her father and his criminal ways, so she would go out and leave clues to help Batman and Robin catch him, spoiling his crimes. However, Stephanie quickly branched out into crimefighting beyond her father and she no longer did any "spoiling", she would directly intervene and fight crime herself. She retained the name for years, not counting her brief tenure as the fourth Robin, and there became such a disconnect between her current activities and her original actions that even a lot of her fans did not know where her identity came from. In 2009, following the death of Batman, she inherited the Batgirl title from Cassandra Cain and the Spoiler identity was laid to rest.
DC Comics' World's Finest title has traditionally been a Superman-Batman teamup book. It evolved out of a 1940s World's Fair special comic.
The Marvel Comics line 2099 showcased the future of the Marvel Universe, including future versions of classic heroes. Initially, the comics took place in the year 2099. Instead of straining the confines of Comic Book Time, Marvel allowed the titles to mention months and years going by, thus the titles eventually took place in the year 2100 and beyond.
The title of the graphic novel series 30 Days of Night refers to the period during the winter in Barrow, Alaska, during which the sun doesn't rise for 30 days straight. In the series, a legion of vampires takes advantage of this to go on a 30-day feeding frenzy without worrying about the sun. The series went on to take place in locations other than Alaska, but retained the title. The events in Barrow set most of the rest of the series in continuous motion by making vampires in danger of being exposed because of the huge massacre in Barrow. So it's partially justified in that the events in the first installment remain important as the series goes on.
The League of Extraordinary Gentlemen retains its title up until the very end, even though the eponymous League was officially disbanded sometime between the events of Century: 1910 and The Black Dossier. By the end, the main cast has ceased to be a "league" and become a dwindling "trio".
In a more general sense, the title of the series was originally supposed to reflect its Victorian setting, since it's the kind of name that a superhero team would have chosen for itself in the late 19th century. Said Victorian setting has been out the window since The Black Dossier (which took place in The Fifties), with the last two installments taking place in The Sixties and the 2000s, respectively. The name simply remained the same because, in-universe, there was no actual reason to change it.
In the 1940s, Fiction House had a series called Werewolf Hunter, featuring Professor Armand Broussard, an Occult Detective. While his first appearance had him facing a werewolf, most of his subsequent stories had nothing to do with werewolves.
In his early stories, Desperate Dan was something of a villain, hence his title. However, Characterization Marches On, and he soon developed into a likeable doofus with super-strength, about as far from a desperado as you could get.
Suzie Comics published by Archie Comics in The Forties and The Fifties originally focused on the titular heroine - a beautiful but ditzy young woman who was forever losing jobs due to her ineptness. She eventually gained a friend called Ferdie (who ranged between Unlucky Childhood Friend and actual boyfriend depending on the issue) who slowly came to dominate the comic. By the time the comic ended in 1954 it was still named after Suzie and she continued to appear on the cover but Ferdie was the real star with Suzie largely resricted to playing his Straight Man love interest.