How Can You Find Out If Someone Has Changed Their Name. How Common Is It For People To Change Their Name And What Might Be The Effects On Someone's Emotion Health Who Does This?

My neighbour has behaved violently and abusively towards me since I moved here 3 years ago...I have recently found out they have moved homes several times due to neighbours..I also have found out he has changed his name....Can you tell me how I can find out about this individual's past criminal record?