Genesis 41:51, 52 And Joseph called the name of his firstborn Manasseh: For God, said he, hath made me forget all my toil, and all my father’s house. And the name of the second called he Ephraim: For God hath caused me to be fruitful in the land of my affliction.
The naming of children in the OT was always significant of some meaning, often about something going on at the time of birth or about hopes for the future. In the case of Joseph’s children born in Egypt, he used the naming of his sons to express his thanksgiving for what the Lord has done for him in the recent past. His response to God blessing him with sons was faith in and thanks to his faithful God.
Manasseh sounds like the Hebrew word for making to forget. God had blessed him so much and lifted him so high that the love, grace and goodness of God was so overwhelming so as to drown out past sorrows and troubles. And the blessing of God was so powerful so as to cause him to forget past offenses and injustices. When we hear the Gospel of forgiveness and grace it causes us, too, to forget all past (and even future) sins and trespasses done by us and to us. Guilt and Grudges are forgiven and forgotten. And the Good News is: God forgets!
Ephraim sounds like the Hebrew word for making fruitful. He praises God for His blessing and for making him fruitful in the land of his affliction. He acknowledges that it was God, not himself, that made him useful and productive through slavery and imprisonment. And, because God did all this for him he was able and willing to forgive, save, and restore his brothers. We also are blessed and made fruitful in the land of our affliction (the world), enslaved to sin and imprisoned by death and the devil. But our Lord intervened, freed us, and set us on high with Christ. Therefore, we give God thanks and praise.