In Judges 12, the Gileadites find a way to distinguish between friend and foe by compelling captured refugees to say the word 'Shibboleth.' Evidently, Ephraimites couldn't pronounce it correctly, saying instead 'Sibboleth.' Those that said that latter were struck down while those who said the former were allowed to pass.
'Shibboleths' abound in society, including among Christians. Unfortunately, even among Christians, a Shibboleth isn't simply a quick way to distinguish where a person stands in relation to you but is used in a manner akin to the Gileadite's use, thankfully, of course, without the resulting slaughter.
Every denomination has their own Shibboleths. I don't want to give examples out of fear of unduly offending some Christian here or there- and also because my own examples would be construed as a Shibboleth and I could become a victim of the very same phenomena I am referencing!
However, I can give you examples from outside of Christianity. For example, a good Muslim, after saying the name Mohammed, will add "Peace be upon him." Jews will write 'God' like this: G-d. These are simple examples.
More complicated ones exist, where terms and phrases thrown out in conversation represent whole concepts and arguments and positions cherished within the speaker's faith tradition. A person outside that faith tradition will hear the terms and phrases but, ignorant of the concepts that are evoked, will construe them differently and further conversation will alert the other that 'They don't really get it. They aren't in my group.' FULL POST 