Thieves' Cant

This way of speaking can be done using any language, any script, hand motions, or just impromptu pictures that have been scrawled on a table with a knife.

In a similar way to Druidic, this is not a language that can be learned through mere study but rather it is learned through experience by those that have spent their lives on the streets, in the criminal underworld or in the shadows committing actions that few of us would dare to think of.