Shibboleth is any usage of language which could be used as an indication of the user’s origins, nativity, or in some cases even affiliation to a certain group. It doesn’t seem to be the same as jargon, argot or cant, because the user seems to have more of a problem disguising the former than the latter three. This article shows a lot of similar such usage in times past and present, in almost all languages in the world, mostly related to how certain specific words can be used to clearly separate a native speaker from someone who just learned the language, because of an overwhelming number of a specific sound that is hard for non-natives to produce, and so forth. Very interesting read.