Asking Google Maps for walking directions between fictional locations from Lord of the Rings produces this "easter egg" response, quoting a character's warning from the story.
An Easter egg is an intentional inside joke, hidden message, or feature in a work such as a computer program, movie, book, or crossword.
According to game designer Warren Robinett, the term was coined at Atari by personnel who were alerted to the presence of a secret message which had been hidden by Robinett in his already widely distributed game, Adventure. The name has been said to evoke the idea of a traditional Easter egg hunt.
This practice is similar in some respects to hidden signature motifs such as Diego Rivera's including himself in his murals, Alfred Hitchcock's legendary cameo appearances, Fritz's appearances in the works of Chris van Allsburg, and various Hidden Mickeys that can be found throughout the various Disney Parks.
Atari's Adventure, released in 1979, contained the first video game "Easter egg" to be discovered by its players, being the name of the game's programmer, Warren Robinett. In 2004 an earlier Easter egg was found in Video Whizball, a 1978 game for the Fairchild Channel F system, displaying programmer Bradley Reid-Selth's surname.