Google just hit a pretty big milestone, having reached the age of legal maturity in the U.S., at 21 years old.

To celebrate, they’ve gifted themselves one of their ubiquitous Google Doodles, and has taken the opportunity to discuss exactly where the word “google” came from, and what actually means. It’s a pretty fun read:

In Friday’s Google Doodle, Google celebrates its own 21st birthday. Google is old enough to drink, but what is a “google”, anyway? It’s a very, very large number:

10,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000.

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.