“THOUGH GOD is wholly simple we must still address him with a multitude of names. Our mind is not able to grasp his essence. We have to start from the things about us, which have diverse perfections though their root and origin in God is one. Because we cannot name objects except in the way we understand them, for words are signs of concepts, we can name God only from the terms employed elsewhere. These are manifold, therefore we must make use of many terms. Were we to see God in himself we would not call on a multitude of words; our knowledge would be as simple as his nature is simple. We look forward to this in the day of our glory; in that day there shall be one Lord and his name one (Zach. xiv, 9).”
~St. Thomas Aquinas: Compendium of Theology, 24.