Green’s Dictionary of Slang

a psalm recited on the gallows by a criminal who is about to die.

c.1698		B.E. Dict. Canting Crew n.p.: Dismal Ditty a Psalm at the Gallows, also a dull Ballad, or silly Song.
1725		New Canting Dict.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict.
1748		Dyche & Pardon New General Eng. Dict. (5th edn).
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1859		Matsell Vocabulum.
1874		Cairo Bull. (Cairo, IL) 5 Nov. 2/3: [from The Graphic, London] I’vew been inclined to make a change / Since Jerry hopped the twig, / And sang his dismal ditty, boys, / And danced old boss’s jog.