A sub-language invented by the hacker culture during usenet days. Letters would be replaced with numbers to make it harder for non-hackers to search for conversations and pick up on what hackers were doing at the time. It got the name "1337" from the word "elite", which where what hackers were. Unfortunately, script-kiddies caught on, and completely missing the point of 1337, instead began to use it to write EVERYTHING, thinking it would earn them passage into the hacker culture. Little did they know that it actually required knowledge to become a hacker. Now it is openly mocked by the hacker community, making fun of the kids who still use it although it's more than 30 years past it's usefulness, instead replaced by 128 bit AES encryption and the like.