Gudakesha means ‘the conqueror of sleep’. All beings fall
victim to sleep when it overtakes them. Such is the power of this factor in
life. But this ‘bull among men’ (Arjuna) has disciplined himself in such a way
that sleep would come to him only when he made a decision to sleep.
When, where are and how long to sleep were all at his will.
In addition to the self-mastery of this type, he is always a
terror to the foes; he is the subduer of baseness within and without.
A man of his caliber is not likely to beat a retreat.
The name was used by Sanjay to describe Arjuna in Chapter II
verse 9.
Source - The Bhagavad Gita by Swami Chidbhavananda