God had changed Abram name because of what He, God was going to do in and thru Abraham. God was doing a new thing. God also changed his wife’s name from Sarai to Sarah:
Gen. 17:15 And God said to Abraham, “As for Sarai your wife, you shall not call her name Sarai, but Sarah shall be her name. 16 I will bless her, and moreover, I will give you a son by her. I will bless her, and she shall become nations; kings of peoples shall come from her.”
The name Sarai no longer fit. God you shall call her for I will bless her and I will give you Abraham a son by her. She, Sarah not Sarai but Sarah will be the mother of nations, and kings, rulers of counties will come into being through her.
The meaning of the names: