ESV - 9 And Jesus asked him, "What is your name?" He replied, "My name is Legion, for we are many.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
The man sees Jesus coming toward him, runs to Jesus, falls down before him and discloses that he knows who Jesus is. He begged Jesus to not torment him. (The NKJV says, 'he worshipped Him.')
When Jesus asked, 'What is your name,' was he asking the man or was he asking the demon? The demon answers.
I think he asked him to reveal his identity as proof that the man was indeed possessed. It could have been said that the man was acting the way he was out of his own spirit. (We know the whole of it because we have the record in scripture. What about the people who came to see what had happened with the herd of swine, who basically blamed Jesus for the loss of that herd?) Are we for certain that they accepted that the man had been possessed?
What were his symptoms? He was living among the tombs, he showed incredible strength, and he would cut himself. (Samson didn't cut himself and live at the graveyard but he had incredible strength. His strength was a gift from God; this wasn't the case with this man. For some of us, these things need to be spelled out).
We have enough demons in this one man to enter into two thousand pigs and cause them to destroy themselves. Why so many demons in this one man?
Here's the thing: I don't believe a man can kill his mom, then go to a local school and shoot 20 six / 7 year olds and 6 teachers without being possessed by at least one evil spirit! But you never hear this said today. I say it on every occasion!
We don't learn the man's name.