Darn good question. Protestant is a label which originates in the protests which led to the reformation in the era of Martin Luther, John Calvin and thereafter. Luther was not the first reformer, just the first who was successful.
Jan Hus, who proceeded him by about a century, is revered by many originalists who consider him the greatest of the reformers. I once attended a very originalist Baptist church who did not consider themselves Protestants because the original Anabaptists of whom Hus was considered a leader, never signed on with the State Church in Rome which was launched with the Nicean Creed in the 4th century. Some of them even consider modern Baptists to be sell-outs and other Protestants to be rebel branches of the Catholic church, which doctrines they also reject.
That’s interesting. I never knew that.
Catholics like to portray that there were never any Christians or Christianity outside the Catholic church and that if it weren’t for the Catholic church, none would exist and neither would Scripture.