"the youngest, the whitest, the most amiable of all - my Benjamin of mice"
The supposedly stolen cup is discovered by Joseph, in Benjamin's bag
Public DomainThe supposedly stolen cup is discovered by Joseph, in Benjamin's bag - Credit: Owen Jones 1869

In Jewish, Christian and Islamic tradition, Benjamin was the last-born of Jacob’s twelve sons, and the favourite among all his brothers. 

The rather more famous Joseph was Jacob's favourite - making his brothers (except young Benjamin) jealous and vindictive.

Benjamin translates as son of right, as in son of my right hand, and the name is associated with strength and virtue.