Where did 1337 speak come from?

Answer 1

Leet originated within bulletin board systems in the 1980s,[1][2] where having "elite" status on a BBS allowed a user access to file folders, games, and special chat rooms. One theory is that it was developed to defeat text filters created by BBS or Internet Relay Chat system operators for message boards to discourage the discussion of forbidden topics, like cracking and hacking.[1] However, creative misspellings and ASCII-art-derived words were also a way to attempt to indicate one was knowledgeable about the culture of computer users. Once the reserve of hackers, crackers, and script kiddies, leet has since entered the mainstream.[1] It is now also used to mock newbies, or newcomers, on web sites, or in gaming communities.[3] Some consider emoticons and ASCII art, like smiley faces, to be leet, while others maintain that leet consists of only symbolic word encryption. More obscure forms of leet, involving the use of symbol combinations and almost no letters or numbers, continue to be used for its original purpose of encrypted communication. It is also sometimes used as a script language.

Taken from Leet wiki

Answer 2

1337 speak, also known as leetspeak, originated in the early days of the internet among hacker and gaming communities as a way to obscure messages from non-technical individuals and add a sense of exclusivity to their communication. It involves replacing letters with numbers or special characters that resemble them, such as using "3" for "E" or "@' for "A." Over time, leetspeak has evolved and is now used for fun, irony, or nostalgia in various online communities.