Maybe the earliest printed reference, from G. Valentine Williams, "With our Army in Flanders" (London, 1915):

“The Regular generally marches in silence. If he sings it is as often as not one of those soldier songs of obscure origin like ‘The Song of Shame,’ which I have often heard sung but have never seen in print. It deals with the misfortunes of a lass that loved not wisely, but too well, and beginning,

         ‘She wuz pore but she wuz honest,’

continues through any number of more or less unprintable strophes.”