Green’s Dictionary of Slang

goth n.

a fool.

1824		Annals of Sporting 1 Mar. 177: The cockneys cried out, ‘Go it, Spring,’ / And then the Goths broke in the ring.
1835		G. Kent Modern Flash Dict. 15: Goth, A – a fool, an idiot.
1848		Flash Dict. in Sinks of London Laid Open.
1857		T. Hughes Tom Brown’s School-Days (1896) 270: Why, you Goth! ain’t we to take the benefit of wisdom, and admire and use the work of past generations?
1989		H. Rawson Dict. of Invective (1991) 12: Negative connotations have become attached to Goth, Hun, Philistine, Vandal, and the names of other peoples.