E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
One who carries butter, eggs, and poultry to market; a packman or huckster. From cadge (to carry). Hence the frame on which hawks were carried was called a cadge, and the man who carried it, a cadger. A man of low degree.
Every cadger thinks himself as good as an earl.McDonald: Malcolm, part ix, chap. xlv. p. 183.