Germany occupied the English island of Jersey during World War II. They found a secret language that was impossible to understand.
Only 1% of the island's just over 100,000 inhabitants still speak Jerseyese fluently. The Government of Jersey declared it an official language in 2019, along with French and English. The discredit of being the "peasants' language" meant that Jerseyese was already discredited during the Second World War, says François Lemaistre, a former Jerseyese teacher.