guilderhead, n. — Green’s Dictionary of Slang

guilderhead n.

[Scot. guldie, ‘a tall, black-faced, gloomy-looking man’ (EDD) + -head sfx (1)]

(Ulster) a stupid, clumsy person.

1983

P. Devlin All of us There 160: ‘And by Christ,’ Feley said, ‘it’ll be the last for I’ll have the greath off the guilderhead fornenst it.’.