Augustine of Hippo

However, a question arises here which should not be passed over and which may perhaps also, quite independently, be bothering some of you. What does it mean, that when the name of Abraham, this man Jacob's grandfather, was changed (he was previously called Abram, you see, and God changed his name and said, you shall not be called Abram, but Abraham)? From that time on he was never called Abram. Search in the Scriptures, and you will see that earlier on, before he received another name, he was only called Abram. …

Sermon 122.4 ↗

Ambrose of Milan

For a name is changed, with a letter added, so that he would be called Abraham instead of Abram, which means 'father of a multitude', as the Latin interpretation has it, or 'sublime father', 'chosen father'; or so that he would become a father and the father of a son. He was vain when he did not know God; he became chosen after he knew God. He was a father when he had offspring by a slave woman; but he was not the father of a son, because he did not have a son who was conceived in lawful marriage. …

On Abraham ↗

Jerome

And your name shall no longer be called Abram, but your name shall be Abraham, for I have made you the father of many nations. The Hebrews say that God, from his name, which is the Tetragrammaton among them, added the letter He to Abraham and Sarah: for he was first called Abram (), which means lofty father, and later he was called Abraham (), which means father of many: for what follows nations is not part of the name, but is understood. …

Hebrew Questions on Genesis ↗