The first words of the Summa Contra Gentiles express an important principle for those who seek the truth: The usage of the multitude…is to be followed in giving names to things. This is important for at least a few reasons that I can think of.
Preeminently it is important for the sake of communication. If I play Humpty Dumpty all the time, there is going to be a world of Alices who won’t want to have anything to do with anything that I say. Communication is hard enough when we use words according to their accepted meanings.
Associated with this is the matter of common courtesy. If I want someone to listen to something that I have to say, then it’s simply a matter of showing respect for the time he spends listening to me and considering what I’ve said that should drive me to extend him the courtesy of trying to communicate as clearly as I can. And that means in part that “the usage of the multitude…is to be followed in giving names to things.” But courtesy is just the Golden Rule in practice, and that means that it is an expression of charity toward my fellow man to speak clearly, and to avoid affectations (like playing Humpty Dumpty) that make it harder for him to understand what I’m saying. At the very least we shouldn’t be surprised to find that we sometimes need to define our terms.