From Wiktionary, the free dictionary
From mad + head.
madhead (plural madheads)
- (slang) A crazy person.
2015, Paolo Hewitt, Getting High: The Adventures of Oasis:'Fuck off, you madhead,' Liam shouted, ducking the objects, but a huge smile breaking out on the singer's face.
2020, Drew Magary, Point B, page 133:“Why should I tell you, you madhead?”