Old English plante "young tree or shrub, herb newly planted," from Latin planta "sprout, shoot, cutting" (source of Spanish planta, French plante), perhaps from *plantare "to drive in with the feet, push into the ground with the feet," from planta "sole of the foot," from nasalized form of PIE *plat- "to spread, flat" (see place (n.)).
Broader sense of "any vegetable life, vegetation generally" is first recorded 1550s. Most extended usages are from the verb, on the notion of "something planted;" e.g. "construction for an industrial process," 1789, at first with reference to the set-up of machinery, later also the building; also slang meaning "a spy" (1812). Many of these follow similar developments in the French form of the word. German Pflanz, Irish cland, Welsh plant are from Latin.