Exodus 3: 13 Then Moses said to God, Indeed, when I come to the children of Israel and say to them, The God of your fathers has sent me to you, and they say to me, What is His name? what shall I say to them? 14 And God said to Moses, I AM WHO I AM. And He said, Thus you shall say to the children of Israel, I AM has sent me to you.
At the end of Matthew, we do know his name, for Christ tells the apostles: “Go therefore to all the nations, baptizing them in the Name of the Father, and of the Son and of the Holy Spirit.”