In blessing Yosef’s sons Yaakov adds the words VEYIKAREH BAHEM SHEMI VESHEM AVOTAI AVRAHAM VEYITZCHAK, “…and let my name be declared upon them and the names of my fathers Avraham and Yitzchak…”. (Gen. 48,16) He was blessing Yosef’s sons. Why was it necessary to mention the name of his grandfather and the name of his father?
We must remember who Josef’s sons were. They were men who grew up in Egypt and specifically in a royal household. Their acquaintances were certainly Egyptian dignitaries. Much of their thinking must have been influenced by Egyptian culture although Josef certainly raised them with Jewish ideals and practices.
This is what concerned Yaakov. He wanted to make sure that these two grandchildren who grew up in Galut and studied Egyptian mores and traditions would not be swayed away from Jewish conviction and faith. To assure this he emphasized the importance of having Jewish names. This he did by invoking the names of his predecessors, Avraham and Yitzchak.
Yaakov realized that when Jews retain their Jewish names they will also retain their Jewish way of life. The name is a shield against the outside influences that have a powerful attraction to draw one away from his Jewish roots.