“Leet (or "1337"), also known as eleet or leetspeak, is a system of modified spellings used primarily on the Internet. It often uses character replacements in ways that play on the similarity of their glyphs via reflection or other resemblance. Additionally, it modifies certain words based on a system of suffixes and alternate meanings. There are many dialects or linguistic varieties in different online communities.
“The term "leet" is derived from the word elite, used as an adjective to describe formidable prowess or accomplishment, especially in the fields of online gaming and computer hacking. The leet lexicon includes spellings of the word as 1337 or leet.
“Leet originated within bulletin board systems (BBS) in the 1980s, where having "elite" status on a BBS allowed a user access to file folders, games, and special chat rooms. The Cult of the Dead Cow hacker collective has been credited with the original coining of the term, in their text-files of that era. 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. Creative misspellings and ASCII-art-derived words were also a way to attempt to indicate one was knowledgeable about the culture of computer users.” | 
