Green’s Dictionary of Slang

to snuffle.

c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Snoach, to speak through the Nose.
1788, 1796		Grose Classical Dict. of the Vulgar Tongue (2nd, 3rd edn) n.p.: To Snoach. To speak through the nose, to snuffle.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.