Although circumventing content filters is a relatively new phenomenon, the use of coded terms to conceal one's meaning is not.
For example, the 19th-century Russian satirist Mikhail Saltykov-Shchedrin made use of "Aesopian," or allegorical, language. He and others used it to circumvent censorship in Tsarist Russia. For example, the forbidden term "revolution" would be replaced with a phrase like "the big job."
Many subcultures have developed their own private codes that are only really understood by in-group members. These are referred to by a variety of names, such as argot, cant or slang.
Polari was a private language used by gay men in early 20th-century Britain, at a time when public sentiment against homosexuality was running high. "Rough trade," for example, referred to a working-class sex partner.
Rhyming slang has also been employed to obfuscate one's meaning to outsiders. A term like telephone, for example, can be replaced by a rhyming equivalent, such as "dog and bone," and then shortened to "dog." In this way, a member of a gang could publicly request that another member call them, and do so even in the presence of the police.
Cockney rhyming slang, which emerged in 19th-century London, is perhaps the best-known example, although there are several others.
Leetspeak evolved in the 1980s, as intrepid internet pioneers ventured online to use bulletin board systems. Some of the workarounds they created to evade moderation are still being used today on sites like TikTok.
This form of linguistic subterfuge typically involves using numbers and symbols as stand-ins for letters. "3" resembles a backward capital E, "1" looks like a lowercase l, "$" can take the place of the letter s, and so on. The term "leet" itself is often written as "1337."
Although it's most commonly used when writing about sex, algospeak has also proven useful in other contexts. For example, it was employed last year in Iran by those protesting the government's crackdown on dissent. Creative misspellings like "Ir@n" were pressed into service to evade censorship.