Green’s Dictionary of Slang

foolish, stupid.

1532		More Confut. Barnes in Works VIII 736/1: Thys felowes folishe apishenesse, and al hys asseheded exclamacions [OED].
1584		Three Ladies of London II: Come giue me my ladies gowne thou assheaded elfe.
1592		Nashe Pierce Pennilesse 29: They are an arrogant Asse-headed people.
1609		Douland Ornithop. Micrologus 65: Asse-headed ignorance [OED].
1830		W.H. Williams Wreck II i: You pauper-fed, ass-headed, bull-faced beadle.