The co-creator of Dungeons & Dragons released numerous tabletop RPGs in his life, but he wasn't always able to pick their name, as the threat of legal action prevented him from releasing another game with the D&D initials.
Dungeons & Dragons has had a controversial history, with numerous accusations of promoting satanism and court cases alleging that the game was a motive for committing murder. Dungeons & Dragons has also had its fair share of legal troubles, including with the owners of The Lord of the Rings franchise. The creators of Dungeons & Dragons removed elements from Middle-earth due to legal threats, which is just one example of outside influences forcing the game to be changed.
Dungeons & Dragons was created by Dave Arneson and Gary Gygax, but ownership of the game would pass on to other individuals and organizations throughout its lifespan. Dungeons & Dragons was published by a company called TSR in the '80s. TSR's financial issues caused Gygax to leave the company in '86 and he went on to help form New Infinite Productions, which released different games until it went bankrupt in '89. One of the games released by New Infinite Productions was called Dangerous Journeys. This name wasn't Gygax's first choice, as he discussed in an interview with The Kyngdoms that he originally wanted to name the game Dangerous Dimensions, but TSR threatened legal action and forced the name to be changed.
Here I enlisted the creative talents of Dave Newton, and between us we produced the Mythus RPG, the second genre of the umbrella system then named Dangerous Dimensions the choice of NEC and JVC from several suggestions I provided. During the process a publisher for a fiction line was lined up and negotiations for other licenses were in progress. Game Designers Workshop was on board as the publisher of the paper RPG. The prototype of the game was shown at the GAMA show in Las Vegas. At that point Williams was informed by her staff at the show that I was about to release a new fantasy RPG. When we heard that TSR objected to the umbrella title, I immediately contacted NEC and JVC to determine if they would object to a name change to avoid a lawsuit one likely to have little merit, but costly. They agreed with my assessment and I changed the umbrella title to Dangerous Journeys. Despite that, TSR sued, attempting to get a temporary injunction preventing release and sale of the new game products. In this they failed.
The objection on TSR's part might seem absurd in hindsight, but they did have a point. Dungeons & Dragons is commonly abbreviated as D&D by fans and releasing another game with two D's in a similar market could have led to confusion if Dangerous Dimensions had taken off. The threat of legal action from TSR also scared off the owners of the Dragon Quest and Final Fantasy series. The first Dragon Quest & Final Fantasy games were changed because of Dungeons & Dragons, so it's no surprise that Gygax wanted to avoid getting into an extended legal battle with the company.
TSR went out of business in '97 and Dungeons & Dragons was purchased by Wizards of the Coast, but there have been other lawsuits involving the movie rights and video games based on the tabletop RPG since then. Despite this, the game is doing better than ever, as 2019 was Dungeons & Dragons' best ever year in terms of sales. Dangerous Journeys wasn't quite as successful and it's doubtful that a double D name would have propelled it to stardom. Dungeons & Dragons was lightning in a bottle and neither of its creators were able to follow it up with anything as influential. Dungeons & Dragons is what people think of when tabletop RPGs are discussed, but that has nothing to do with alliteration.
Source: Gary Gygax/The Kyngdoms