Polari has been included on a list of endangered languages.

The slang, used as a code among some gay people when homosexuality was illegal, is on an online database created by University of Cambridge researchers.

The free website has been developed by researchers at the World Oral Literature Project and includes records for 3,524 world languages, from those deemed “vulnerable”, to those that remain well understood but are effectively extinct, like Latin.

Researchers hope to use it to crowd-source information from all over the world about both the languages and the stories, songs, myths and folklore associated with them.

Polari was originally used by market traders and sailors and some believe can be traced back as far as the 16th century.

It has its roots in English, Italian, Yiddish, canal, theatre and Gypsy languages

Until the 1970s, it was used by a small number of gay people as a private communication method to avoid hostile attention and develop an identity.

Some words, such as ‘naff’ and ‘camp’, are now in general usage.

Of the 3,524 languages listed, about 150 are said to be in an extremely critical condition with the number of speakers in single figures or even just one.

Examples include the Southern Pomo language, spoken by Native Americans in parts of California; Gamilaraay, the language of the Kamilaroi of New South Wales; and the language of the Sami communities based in northwestern Russia.

Languages from the UK include Welsh, Scots, Manx, Cornish and Old Kentish Sign Language.