The Sicilian Vespers began when some French thug in uniform grope a Sicilian wife in front of her husband during the Vespers service before Easter.
Over the next few weeks eight thousand French thugs and non-thugs both were killed in Sicily, and after months of further rebellion the despotic sovereign and his thugs were finally kicked out of Sicily.
I read somewhere that the particular incident you describe gave an “ancient and honored society” its popular name by way of an acronym from a rallying cry.....
Morte Alla Francia Italia Anelo!
(Death to the French is Italy’s Cry)