R2-D2 (pronounced Artoo-Detoo) is a fictional character in the Star Wars franchise created by George Lucas. He has appeared in ten of the eleven Star Wars films to date. Lucas didn’t have to dig too deep to come up with the character’s name; it came, inadvertently, from his own filmography.

The name came about during the time when Lucas was making one of his earlier films, ‘American Graffiti’ (1973). Sound editor Walter Murch states that he is responsible for the utterance which sparked the name for the droid. Murch asked a co-worker for “Reel 2, Dialog Track 2”, using the abbreviated form "R-2-D-2", sort of a verbal shorthand.

Lucas, who was in the room and had dozed off while working on the script for ‘Star Wars’, momentarily woke when he heard the request and, after asking for clarification, stated that it was a "great name" before going back to working on his new script. Lucas recalled the acronym and later introduced the world’s favorite droid in ‘Star Wars: Episode IV – A New Hope’ (1977).

R2-D2 stands for Second Generation Robotic Droid Series-2, according to a Star Wars encyclopedia published after the release of the film Star Wars.

Chewbacca’s name was inspired by the director’s enormous malamute, while Han Solo is a word play on the character, who acts as a lone gunman.

More Info: en.wikipedia.org