plot

First recorded before 1100; the noun has multiple origins: in the sense “piece of ground,” Middle English: “small area, patch, stain, piece of ground,” Old English: “piece of ground” (origin obscure); in the senses “ground plan, outline, map, scheme,” variant (since the 16th century) of plat¹, itself partly a variant of Middle English, Old English plot; in the sense “secret plan” (from the 16th century), by association with complot; the verb is derivative of the noun

1. See conspiracy. 19. Plot, conspire, scheme imply secret, cunning, and often unscrupulous planning to gain one's own ends. To plot is to contrive a secret plan of a selfish and often treasonable kind: to plot against someone's life. To conspire is to unite with others in an illicit or illegal machination: to conspire to seize a government. To scheme is to plan ingeniously, subtly, and often craftily for one's own advantage: to scheme how to gain power.

The word plot has no known origin and exists solely in English. The noun dates from the late 10th or early 11th century and originally meant “a small piece of land or area of ground.” Plot in the sense “a small piece of land in a cemetery” was originally an Americanism and dates from the mid-19th century.
In the mid-16th century, plot was used to refer to a map, ground plan, sketch, or written outline. At about the same time, it also came to mean “a secret, usually evil plan”; the verb meaning “to plan secretly, devise” comes from that sense of the noun. Plot in the sense “a storyline or main story of a play or novel” dates from the early 17th century.