During WWII German occupation of the Nederlands, the Dutch used Scheveningen (a seaside town near Den Haag) as a shibboleth to tell Germans from Dutch because Germans

Also if you watch Band of Brothers, the Allied forces use "Flash" / "Thunder" as sign/counter sign (call and response) to verify each other. The reason is because Voiceless dental fractives (th) are rare in German

During WWII German occupation of the Nederlands, the Dutch used Scheveningen (a seaside town near Den Haag) as a shibboleth to tell Germans from Dutch because Germans

Also if you watch Band of Brothers, the Allied forces use "Flash" / "Thunder" as sign/counter sign (call and response) to verify each other. The reason is because Voiceless dental fractives (th) are rare in German 

https://en.wikipedia.org/wiki/Voiceless_dental_fricative

I find Shibboleths to be very fascinating

creating and destroying; built flying cars & autonomous vehicles, now building /faust, more here: /july, web: july.rocks

Here's a classic shibboleth from Inglorious Bastards, that's also become a meme about violating a shibboleth

I find Shibboleths to be very fascinating

https://en.wikipedia.org/wiki/Shibboleth

in san francisco the classic ones were
frisco
san fran
cali

my fave example of this is from The Battle of the Golden Spurs between French and Flemish in 1302 Bruges

Their shibboleth could have been shibboleth 

First time I heard of shibboleth was in a West Wing episode—I also find it so interesting.

I have Belgian family and they also recount that the Belgians used the words “schelde” and “vriend” to tell native speakers from foreigners in the war.

After 20 years trying out those words at the holidays, I still wouldn’t make it 😆