Okay, so a long time ago in 1937, there was a really bad thing that happened in a country called Haiti. There were some people called Haitians who didn't like other people called Dominicans. The Haitians and Dominicans didn't get along because they were from different countries and had different languages and cultures.
One day, some bad guys in the Haitian government gave orders for soldiers to attack a town in the Dominican Republic called Parsley. The soldiers went around the town and asked people to say a word in Spanish. If they said the word wrong, the soldiers would kill them with a machete (which is a big knife). The word they picked was "perejil," which means "parsley" in Spanish. But the Haitians pronounced it differently than Dominicans, so the soldiers used that as an excuse to hurt them.
Lots of people were killed in the attack, and it was really scary and sad. It's called the Parsley Massacre because of the word the soldiers used to identify who they wanted to hurt. It was a really bad thing to do, and we should always remember it so that we can learn from the past and be kind to each other in the future.