Definition from Wiktionary, the free dictionary
addlehead (plural addleheads)
- (colloquial) A foolish or dull-witted person.
1854, Samuel Byron Brittan, The Spiritual Telegraph, volume 3, page 131:
- Those reverend addleheads, convinced of the genuine character of the communications, but with their "dominant idea," the devil, in their heads, summoned his highness the prince of darkness to give an account of the matter.