Also, what is the history of use and what languages do they come from? Is it a fitting name today or is it outdated? How do the two relate to each other?
Catholic can have a few different meanings. It could refer to:
The Nicene creed which is used in a lot of Christian churches that have broken away from the Roman Catholic church still say that they "believe in one holy and catholic". (note the lower case letter 'c' in catholic.) Catholic in this context does not refer to the Roman Catholic church, but to a holy Universal church.
Protestant refers to churches and/or individuals who call themselves Christians, but disagree with the Roman Catholic Church.
They generally follow the teachings of leaders of the reformation (e.g. Luther). They are called Protestant because they protested the teachings of the Roman Catholic church. The original Protestant movement came from within the Roman Catholic church. The teachings of the protestant movement disagree with Roman Catholicism and a number of the reformers were put to death because they taught these things.
Do these terms still fit today? I don't think this can be answered objectively, but I feel that they are still a correct fit. Mainstream Protestant denominations still hold to the Five Soli. From my understanding, these beliefs do not fit with the Roman Catholic church teachings and so Protestants are still protesting the Catholic Church
The word "Catholic" is an old term meaning "universal." For this reason, even non-Roman Catholics still confess in the Nicene Creed that they believe in "one holy apostolic and catholic church." As Roman Catholics consider their church to be the one true church descended from Peter, this makes sense. Based on the confession of St. Peter, they believe that they alone have "the keys to heaven," and that grace can be conferred within the church for the forgiveness of sin.
Protestants, typically beginning with Martin Luther in 1517, have "protested" this claim to universality. Specifically, they tend to deny that the Pope- the leader of the world's 1.2+ billion Catholics, is in fact the earthly head of the church. (Oddly enough the same protest the Eastern Orthodox have had since the beginning of the church, but formalized with the agreat Schism in 1054). In contrast, Protestants typically believe the Pope to be an important leader, but not the leader, outside of whom there is no means by which grace can be conferred.
Protestant refers to groups which originated in protest of many beliefs that (they felt) lead to the authoritative and tyrannical nature of the Catholic Church of the era which spanned hundreds of years. Some people call Protestants the reformers, but it should be noted that the Catholic Church has gone through major reform as well since the era.
The major difference between Catholics and Protestants is that original Protestants believed true knowledge of God came from the Holy Spirit alone through the Holy Bible alone, specifically through personal study of the Scriptures as opposed to being taught within structured and institutionalized organizations which they viewed the Catholic Church as. This isn't meant to discredit modern Churches, it was just seen a major factor in how the Catholic Church was able to work outside of God's word during the era.
The word 'Catholic ' is still fitting since much of Catholicism has remained the same. The term Protestant however has become very generalized, to the point that few groups that refer to themselves as Protestants share exactly the same beliefs, and many Protestant groups follow greatly different beliefs.