Here's an example: a group of my friends has a term we invented. It's a verb that means "to pronounce over-correctly", used of a word borrowed from another language when that word has a common anglicized pronunciation, but the speaker of the word chooses instead to pronounce in the source language. There may be a standard English word that has this same meaning, but our private word is derived from the name of a person we know who does this often, and so it's sort of an inside joke: "Oh, stop Trauthing, you pompous fool."
The word I'm looking for describes such a private word. Sort of like a single word in an idioglossia but with no surrounding language; the private word stands on its own. Taking a cue from neologism I might coin the word idiologism but that word apparently already exists (or so says google) and has a slightly different meaning since it's only used by one person.
Is there a word for a coined, private word, which has a specific meaning only to a certain small group of people?