Brochas Daf Yud Gimmel amud aleph

“Avram is Avraham.  At first he became father to the nation of Aram, and ultimately he became father to the whole world.”

Rashi explains Avraham is a contraction of Av Hamon, father of a multitude, as is stated in Bereishis 17:5 “For I have made you father of a multitude of nations.”

The Maharsha comments based on Gemara Nedorim that there was a two stage process in changing his destiny.  First Avram left his land and merited a son, Yishmael, at which point he took on the designation of father of a single nation.  However, by changing his name, his ‘mazel’ was transformed to the extent that as Avraham he became father of nations, because each and every tribe within Israel is designated “goy v’khal goyim.”