If you use Google all day, every day, you might have noticed today’s Google Doodle. Google celebrates its own 21st birthday. Google is old enough to drink, but what is a “google”, anyway?Well, it’s a very, very large number. A one, followed by a hundred zeroes, which is what you get if you multiply ten times ten and keep multiplying by ten until you’ve done it a hundred times. Google founders Larry Page and Sergey Brin borrowed the term for their company in 1998, to suggest the unfathomably large number of results their new search engine could provide. Page and Brin were obviously exaggerating a bit, and they also took a bit of poetic license with the spelling.And if you’ve always thought Google’s name sounded like a nonsense word made up by a small child, that’s because it actually was: then-nine-year-old Milton Sirotta, whose mathematician uncle Edward Kasner asked him to pin a name on the enormous number for a book Kasner was working on published in 1940.