Krishna has many names because each name signifies some different quality of his and teaches us something. For example, "Hrishikesh" means one who controls the organs. From this name we have to learn that we should also control our organs.                          

The same is true of Arjuna's many names. Because Arjuna has a lot of good qualities in him, we gave him many names. They are adjectives for us to learn from. 

--Swami Radhanandaji