Cant

A is the language or “jargon” of a group, often employed to exclude or mislead people outside the group. It may also be called a cryptolect, argot, anti-language or secret language. Each term differs slightly in meaning, and their use is inconsistent.

Etymology
There are two main schools of thought on the Terran origin of the word cant:
 * In linguistics, the derivation is normally seen to be from the   word caint (older spelling cainnt) "speech, talk", or  cainnt. In this sense it is seen to have derived amongst the  groups of people in  and, hailing from both Irish/Scottish Gaelic and English-speaking backgrounds, ultimately developing as various s. However, the various types of cant (Scottish/Irish) are mutually unintelligible to each other. The Irish creole variant is simply termed "". Its speakers from the  community know it as Gammon, and the linguistic community identifies it as Shelta.
 * Outside Goidelic circles, the derivation is normally seen to be from Latin cantāre “to sing” via canter. Within this derivation, the history of the word is seen to originally have referred to the chanting of friars, used in a disparaging way some time between the 12th and 15th centuries. Gradually, the term was applied to the singsong of beggars and eventually a criminal jargon.

Argot
An argot (from argot  ‘slang’) is a language used by various groups to prevent outsiders from understanding their conversations. The term argot is also used to refer to the informal specialized vocabulary from a particular field of study, occupation, or hobby, in which sense it overlaps with.

In his 1862 novel , refers to that argot as both “the language of the dark” and “the language of misery.”

The earliest known record of the term argot in this context was in a 1628 document. The word was probably derived from the contemporary name les argotiers, given to a group of thieves at that time.

Under the strictest definition, an argot is a proper language with its own grammatical system. But such complete secret languages are rare because the speakers usually have some public language in common, on which the argot is largely based. Such argots are lexically divergent forms of a particular language, with a part of its vocabulary replaced by words unknown to the larger public; argot used in this sense is synonymous with cant. For example, argot in this sense is used for systems such as ' and ', which retain French syntax and apply transformations only to individual words (and often only to a certain subset of words, such as nouns, or semantic content words). Such systems are examples of argots à clef, or "coded argots."

Specific words can go from argot into common speech or the other way. For example, modern loufoque ‘crazy, goofy’, now common usage, originates in the  transformation of Fr. fou ‘crazy’.

In the field of medicine, physicians have been said to have their own spoken argot, cant or slang, which incorporates commonly understood abbreviations and acronyms, frequently used technical s, and much everyday professional slang (that may or may not be institutionally or geographically localized). While many of these colloquialisms may prove impenetrable to most lay people, few seem to be specifically designed to conceal meaning from patients (perhaps because standard medical terminology would usually suffice anyway).

Thieves' cant
The thieves' cant was a feature of popular pamphlets and plays particularly between 1590 and 1615, but continued to feature in literature through the 18th century. There are questions about how genuinely the literature reflected vernacular use in the criminal underworld. A thief in 1839 claimed that the cant he had seen in print was nothing like the cant then used by gypsies, thieves and beggars. He also said that each of these used distinct vocabularies, which overlapped, the gypsies having a cant word for everything, and the beggars using a lower style than the thieves.

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