In plain words
The world holds many things, and each has its own name. But no one at all can say why this particular thing has this particular name -- it is not even possible to say. And if one does try, that is merely their own guesswork, and cannot be the truth. Everything is by divine decree and nothing else; blessed are those who recognize this. Whether it be the terms that exist from the moment of birth to the moment of death, or those that exist before birth or after death, or the words 'mother' and 'children', or 'Dharma', 'adharma', 'heaven', 'hell', 'brāhmaṇa', 'vaiśya' and the like -- human beings did not create these words, absolutely not, not at all; and it is the Vedas alone that stand as authority for saying so.
Let us consider one point. Can anyone at all show a word that has only a word and no meaning, existing anywhere in this world or in any other? They cannot show it; it is not possible. Therefore, it is only when human beings recognize that every word has a meaning, and that this meaning is a divine decree, that they can come to know the secret of life.
So whether one says 'the brāhmaṇa was His mouth' or 'the fourfold order was created by Me, by the division of guṇa and karma', there must indeed be the varṇas indicated by the meanings of the words in those verses, and persons who are the proof of them, mustn't there! 'I Myself have been creating these persons in accordance with their guṇa and karma' --