Shibboleth

shibboleth
/ˈʃɪbəlɛθ/
noun
  1. a custom, principle, or belief distinguishing a particular class or group of people, especially a long-standing one regarded as outmoded or no longer important.
    “the majority, under the influence of vague nineteenth-century shibboleths, understood him to be associating himself with the doctrine that every nation has a right to be a sovereign state”

    My hubby used this word, so I asked him what it meant. He said something vague then said ‘look it up, I’m not sure’ so I did!

    I’m not sure I’d ever dare use a word like that!