Languages: Cants (Thieves & Other)

Working on Creatures & Catacombs today and finally realizing this is definitely not going to end up the minimalist dream I'd originally intended.  While trying to give at least a little description to the various PC races, the idea of language came up, and I started wondering if I should include Thieve's Cant.  This further got me wondering what the heck a "cant" even is.

Wikipedia turned up the definition:

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

This was frankly fascinating.  It inspires the idea of sub-languages spoken by various in-groups concealing the secret or semi-secret in broad daylight.  Not sure I'll manage to include this gracefully when running my own sessions, but I'd like to put the idea in there so it's available if I need it.  The real temptation is to give everyone their choice of one cant at character creation, and the ability to pick up another later in place of a language.

Text following is what I have to put in the game so far:

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Cant employs the subtle use of phrase, tone, sign and word choice by a given social group to obscure outsider understanding of their communication.  These “cants” overlap with language: Often individuals must speak at least one mutual language to also use a cant.  Taking the Savvy skill grants a character proficiency in one type of cant, and can be used in an attempt to guess the meanings of other cants. Proficiency in additional cants requires a language slot.  Examples include:

• Club Talk – Phrases and gestures used among elite clubs and secret societies.

• Crim (Thieve's Cant) – Specific to gangs and those who deal frequently with organized criminals.

• Ivory Parlance – Used by academics and intelligentsia. Peppered with obscure phrases in other languages, using passing reference to classics and obscure theories as a form of shorthand.

• Professional Jargon – Used by traders and crafts professionals to notify or warn each other.

• Salt Speak – Used by sailors and those who deal with them.

• Society Speech – Protocols, intimations and subtle jabs used among the upper crust.

• Soldier Speak – Military jargon, trumpet, drum and hand gesture used to direct troops.

• Vagrant Code – Used by tramps, hobos and others itinerants. Includes many symbols to point the way to food, shelter, work and many forms of danger.

• Vulgar Argot – Used by the servant and lower classes, but not specifically criminals.