Shibboleth:   Judges 12:1-4 describes an interesting moment in the history of Israel.   The people of Gilead had gone to war with the Ammonites, but had selfishly not invited their neighbour from Ephraim.   This made the Ephraimites, who were always up for a bit of fight, really mad.   So they fought, but the Gileadites were stronger and the Ephraimites ran away.   This may explain why they had not been invited to the Ammonite war in the first place!

The fleeing Ephraimites therefore adopted a clever device when captured to avoid death and slaughter.   When asked "are you an Ephraimite?" they replied "Um... no?" (genius)!   Flustered at first, the Gileadites countered by asking them to say the word "shibboleth" which means 1) ear of corn, or 2) flowing stream.   Unfortunately, the Ephraimites could not pronounce this word, saying "sibbolet" instead.   So they were all slaughtered.

Nowadays, of course, this sort of behaviour is rather frowned upon, as it is making fun of somebody's racial or cultural background.   This is the equivalent of asking a suspected Chinese person (or Johnathan Ross) to recite "round the rugged rocks the ragged rascal ran".   Still, these events showed that the men of Gilead were cunning linguists indeed.