means The structured sequence of events in a story, linked by cause and effect — or, separately, a measured piece of ground, or a secret scheme to do something underhanded.

from From Old English 'plot,' meaning a small patch of ground — a marked-off bit of earth. The land sense came first; the others sprouted from it. The 'secret scheme' meaning likely grew from the idea of a marked-out plan or chart, possibly cross-pollinated by the French 'complot' (a conspiracy). From plans on paper came the literary 'plot': the laid-out ground plan of a narrative.