Green’s Dictionary of Slang

nailheaded adj.

[the hardness of a SE nail head]

(US) stupid, stubborn.

(con. 1700s) C.C. Garrason ‘An Update of the late Albert Timothy Outlaw’s Article on Garrison-Williams-Dobson’ Garrason.com 🌐 A descendant, also named Gerret Gerretsen, living sometime in the 1700s, displayed the ultimate in stubbornness. He was famed for it, so much so that he was called Nail-headed Gat by his contemporaries.