Green’s Dictionary of Slang

dunghill n.²

SE in slang uses

In phrases

moving dunghill, walking... (n.)

a notably filthy man or woman.

1771		R. King New London Spy 62: He is so taken up with the passion of gormandizing [...] and may be considered as a firkin of foul stuff, a lump of filth, or walking dunghill .
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Moving dunghill; a dirty, filthy man or woman.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.