Green’s Dictionary of Slang

an old, prob. impotent, man.

[1823		Westmorland Gaz. 9 Aug. 1/5: Compared with his opponent Mr Broadbent, he would be a stuffed eel-skin to a butt of beer [...] or a pop-gun to a battering ram].
1841		D. Boucicault London Assurance in London Assurance and other Victorian Comedies (2001) Act II: I would rather give up all my fortune and marry the man I liked than go to church with a stuffed eel-skin.
1844		Bentley’s Misc. 15 268: His Lordship swaggers into the hall, preceded by a mace-bearer, purse-bearer, or some other foolish fellow, and followed by a stuffed eel-skin in a suit of black, holding up his Lordship’s tail.
1846		Hilpert & Kärcher German Eng. 360/1: A long, lanky, awkward fellow, a fellow all lath and plaster, a bag of bones, a stuffed eel-skin.