Green’s Dictionary of Slang

a spoil-sport who ‘addles’ the ‘plots’ or plans of others.

1696		D’Urfey Boarding School A2: Dramatis Personae [...] Lady Addleplot, A Lust flaunting imperious Lady, a highflown stickler against the government.
c.1698		B.E. Dict. Canting Crew n.p.: Addle-plot, a Martin-mar-all.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1793		J. Caulfield Blackguardiana.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
2023		R. Milward Man-Eating Typewriter 38: [F]ash bats and sharpering-omis were after us, those evil eagle-eeked addle-plots who cruised the city.