After Yosef is released from prison and raised to the stature of second-in-command in Egypt, he gets married and has two sons. He names one son Efrayim, because of his declaration, "Hifrani Elokim Be’eretz Onyi" – "G-d has made me fruitful in the land of my affliction." Through this name, Yosef gives thanks to Hashem for granting him blessing and prosperity in Egypt. After having been driven away from his home and then imprisoned in Egypt, he achieved great success and prestige, for which he was grateful.
The name of Yosef’s second son, Menashe, is more difficult to understand. The Torah says that Yosef chose this name because he said, "Nashani Elokim El Kol Amali Ve’et Kol Bet Abi" – "G-d has made me forget all my travails and the entire house of my father." It appears that Yosef expresses gratitude for his being able to forget his past travails – which is certainly understandable – but also for his forgetting his father’s home. The question is, why is Yosef proud or appreciative for forgetting his home? Didn’t he want to retain his memories and emotional bond with his father? Why would he celebrate his forgetting the nurturing home of Yaakob Abinu?
The answer to this question relates to another question, which was already raised by the Ramban. Why did Yosef not make any contact with his father after being released from prison and rising to power? Once he was in a position of authority, he presumably had the ability to at least send a letter. He knew Yaakob must have been suffering, thinking that he was dead. Why did he make no effort to contact Yaakob to tell him he was alive and well?
Some Rabbis answer that the dreams Yosef had dreamt of his family bowing to him had the status of a prophecy, and it was thus forbidden to interfere with the process of their fulfillment. Yosef knew that if he would immediately notify his family that he was the second-in-command in Egypt, they would not come and bow to him. He realized that he would have to wait until his brothers come and, without recognizing him, bow in humble submission before him. This was the only way for the prophecy to be fulfilled. While we do not necessarily understand why G-d wanted the events to unfold in this manner, we do know that Yosef felt bound to ensure the fulfillment of his prophecy. And thus although it pained him knowing that his father was grieving, he had to conceal this information from his family.
This might be the explanation of Menashe’s name. From where did Yosef derive the strength to keep the information concealed? He loved his father so deeply, and felt an overpowering desire to lift him from his sorrow and notify him that he is alive. How was he able to refrain from alleviating his father’s grief? The answer is that he received this strength from G-d, who always provides us with the strength and fortitude we need to overcome life’s tests. He therefore thanked G-d for allowing him to "forget" his father’s home. This does not mean that he lost all mental and emotional bonds with his father. Rather, it meant that G-d gave him the strength to exert control over his natural desire to contact his father. Yosef recognized that this unimaginable personal strength was not his own, but rather came from the Almighty. And he therefore thanked and gave praise to G-d for enabling to carry out his duty, to keep his whereabouts concealed from his father so that the prophecy could be fulfilled.