Steven Levy wrote about this in his book, In The Plex:
In September 1997, Page and Brin renamed BackRub to something they hoped would be suitable for a business. They gave serious consideration to “The Whatbox,” until they realized that it sounded too much like “wetbox,” which wasn’t family-friendly. Then Page’s dorm roommate suggested they call it “googol.” The word was a mathematical term referring to the number 1 followed by 100 zeros. Sometimes the word “googolplex” as used generically to refer to an insanely large number. “The name reflected the scale of what we were doing,” Brin explained a few years later. “It actually became a better choice of name later on, because now we have billions of pages and images and groups and documents, and hundreds of millions of searches a day.” Page misspelled the word, which was just as well since the Internet address for the correct spelling was already taken. “Google” was available. “It was easy to type and memorable,” says Page.
