Random story of the day:

Mapmakers often put secrets in their maps as copyright traps, to make sure no one copies their maps. For example, some map makers put fake streets in maps, sometimes fake features. If they see a map that has that street, they know it was copied from them.

Similarly, in 2005, the New Oxford American Dictionary published a new word: Esquivalience, meaning “Willful avoidance of one’s official responsibilities”. It was a made up word, a copyright trap to make sure no other dictionaries copied them. If anyone copied their dictionary, the stealer wouldn’t be able to come up with a source except for the New Oxford. (Dictionary.com fell for this trap)

Another example of a copyright trap was when the author of The Trivia Encyclopedia put a false fact in his book, because he was certain that the makers of the game Trivial Pursuit were taking his facts for the game. (The false fact was that “TV detective Columbo’s first name was Phillip” when the show never specified his name. Sure enough, the ‘fact’ showed up in Trivial Pursuit.