> The Gileadites captured the fords of the Jordan leading to Ephraim, and whenever a survivor of Ephraim said, “Let me cross over,” the men of Gilead asked him, “Are you an Ephraimite?” If he replied, “No,” 6 they said, “All right, say ‘Shibboleth.’” If he said, “Sibboleth,” because he could not pronounce the word correctly, they seized him and killed him at the fords of the Jordan.
- Judges 12:5
In WW II, a well-known challenge/password/countersign set used by American and British soldiers during the D-Day landings in France was "flash"/"thunder"/"welcome". "Thunder" and "welcome", of course, are words that a German is likely to mangle.