The word “Catholic” means “universal.” Anti-Catholics don’t care for that term, so they invent terms such as “Romanist” or “Roman Catholic” to “localize” the Faith, and diminish the “universal” meaning of the term.
Yes, that’s right - the term “Roman Catholic” is of protestant (and anti-Catholic) origin. The Church does not refer to Herself with this term. The Church simply uses the term, “Catholic.”