On church history:
Back in Luther’s time, Germany was ruled by princes, both Lutheran and Roman Catholic. If Charles V, the Roman Emperor, had his way, he would have forced all of Germany, including all of Europe, to remain Roman Catholic. Six of the princes who ruled Germany had already converted to Luther’s view, including its 14 Free Imperial cities. They considered themselves Evangelicals or Lutherans (or followers of Luther).
Charles V gave to order (Edict of Worms) to enforce all the German lands to remain Roman Catholic But thank God those six Lutheran princes courageously stood together, united and strong, and refused to accept this rule. They protested, made their case to demand that Lutheran lands should be free to remain Lutheran, and where the prince was Roman Catholic, that state may remain Catholic.
Then, on April 29, 1529, the six princes declared to Charles V:
“We protest before God and before men that we and our people will not agree to anything in this decree that is contrary to God, to His Holy Word, to our right conscience, and to the salvation of our souls.”
Charles V could do nothing because the princes stood up in unity for religious freedom. From then on, they were known as the Protestors or the Protestants.