Today in 1517, Martin Luther nailed a paper inscribed with 95 "theses" to the door of the Castle Church in Wittenberg, Germany. It was the formal beginning of the Protestant Reformation.
The theses regarded what Luther saw as moral and ideological degradation in the Roman Catholic Church. His primary grievance was with the "indulgences" system, which permitted Catholics to be absolved of sins through payments of money to the Church. At the time, Price Frederick III had banned indulgences within Wittenberg, but church members were traveling outside of the city to buy them.
Luther's theses were translated into German from Latin, and made their rounds. One copy was brought to Rome. Efforts to curb him failed, and eventually, in 1521, Pope Leo X excommunicated him. That year, Luther was brought before the Holy Roman Emperor Charles V and still refused to redact the theses. Charles had issued the "Edict of Worms," declaring it legal for anyone to murder Luther without consequence. Thankfully, Luther was under the protection of Prince Frederick. Luther then spent a decade translating the Bible into German.
The name "Protestant" was first used in 1529. The Edict of Worms had previously included a clause that permitted rulers of the German states to choose whether or not they would enforce it. Luther's supporters mounted a protest against the now mandatory Edict, saying that their allegiance to God was stronger than their allegiance to the crown.