English
addle-plot
From addle (“to muddle, to ruin”) + plot (“plan”).
The story
In earliest use as a character name in Love for Money by Thomas d'Urfey in 1691.
Today it means
noun Synonym of spoilsport, one who ruins other's plans or enjoyment of something.
Language periods are conventional ranges, not dates for this word.
Etymograph / addle-plot