Green’s Dictionary of Slang

any variety of coloured handkerchief; thus also Kent clout, Kent rag.

1812		Vaux Vocab. of the Flash Lang.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1859		Hotten Dict. of Modern Sl. etc. 55: KENT RAG, or clout, a cotton handkerchief.
1864, 1867, 1870		Hotten Sl. Dict. [as cit. 1859].
1868		Liverpool Mercury 2 Dec. 3/1: In cant a handkerchief would be called a ‘billy’ [...] or a ‘Kent rag’; while in slang it would be called a ‘rag,’ a ‘wipe,’ or a ‘clout’.