Genius in a tiny mother bird, who learned to give her babies a password so they wouldn't die. A musical password. The Superb Fairy Wren sings to her eggs. The unborn baby birds, still in the egg, learn that musical password and sing it on being hatched.
If a shibboleth is a way to determine an "insider", by saying something that only an "insider" could say, what is something that an "insider" would never say? How about a 'Frisco'? [more inside]
"The world wide web was supposed to be pistachio". Say that three time fast, then visit the internet database of tongue twisters, shibboleths, and battologisms; over 2,000 frustrating, word-mangling, syntax-slaughtering entries in 90 languages, with translations. Also worth a look: the short list of devious one-liners.