"- If I were to say to you, 'I am a stranger traveling from the East, seeking that which is lost'...
- Then I would reply that, 'I am a stranger traveling from the West, it is I whom you seek.'"

https://mummy.fandom.com/wiki/Medjai

Is there a technical term for similar "identifier phrases"?

I'm looking for ways for mutual authentication for humans, e.g. over the phone.

@buherator shibboleth?

@stf Didn't know that one, very interesting! Thanks!