Green’s Dictionary of Slang

1. (US) a native of Tennessee.

1838		in H. Rawson Dict. of Invective (1991) 49: mudhead. Also a native of Tennessee (Dictionary of American English, 1838).
1838		T. Haliburton Clockmaker II 264: There’s the hoosiers of Indiana, the suckers of Illinoy, [...] the mudheads of Tennessee.
1843		T. Haliburton Sam Slick in England I 236: Why, as I am a livin’ sinner that’s the Hoosier of Indiana, or [...] the Mudhead of Tennesee.

2. (also mudbrain) a fool [backform. f. mud-headed adj.].

1881		Bulletin (Sydney) 9 Apr. 9/2: ‘Whereabouts you may reside, then, mister?’ To which the mudhead replied [etc].
1887		Bulletin (Sydney) 22 Oct. 8/4: ‘Then what the eternal thingammy have you got a splay-footed old mud-head of a kanaka digging post-holes on your property for?’ yelped the big elector.
1958		R. Chandler Playback 46: Mudheads always bore me.
1990		T. Winton Human Torpedo 8: Wet nappy, mudbrain. I must be the only person in this house who’s heard of the toilet.

3. (W.I.) a native of Guyana, the majority of whom live in the muddy coastal areas of the country; also as adj.

1916		J.G. Cruickshank Black Talk 49: Hassar-soup (said a Mud-head) is ‘sweet too bad’.
1926		E. Walrond Tropic Death (1972) 34: De Bajan man him say [...] plantain an’ salt fish don’t want ’um, an’ de Mud-head man him say, me wish me had ’un. [Ibid.] 172: Oi tell yuh ’bout dese fancy mud-head men! Ent a blind one o’ dem any blasted good!