He has been terrified of snakes from his childhood is possible, although He has been terrified of snakes since he was a child would be more usual. He is terrified of snakes from his childhood would suggest that snakes from his childhood terrify him today, which sounds odd and unlikely. He was terrified of snakes from his childhood would suggest that snakes from his childhood continued to terrify him until recently, which also doesn't sound likely.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.