Green’s Dictionary of Slang

(Irish) an utter fool.

1960		P. Smith Esther’s Altar 58: Just let him wait, Mister Fecky the Ninth, he’d see ! Next time, she’d best him.
2001		G. Coughlan Everyday Eng. and Sl. 🌐 Fecky the Ninth (n): complete idiot.
2010		H.M. Struble Don’t Dance with Mary Grace 167: I am such a ‘Fecky the Ninth’ such a complete nitwit [...] I can’t decide who I love the best.