Why is heavy machinery called "plant"?

Solution 1:

My dictionary suggests:

ORIGIN Old English plante [seedling,] plantian (verb), from Latin planta ‘sprout, cutting’ (later influenced by French plante) and plantare ‘plant, fix in a place.’

My suggestion: It's simply a very big thing which can hardly be moved and hence behaves like a plant, something fixed in place; likely also closely related to the meaning of the verb, "to place or fix in a specific position."

Solution 2:

I suspect it could also stem from the fact that another word for a factory is a plant (e.g. a power plant), the etymology of which is as deceze suggests.

The term could then have evolved to refer to the machinery either produced by or used in the plant ('I'm here to repair the plant machinery'), which was then shortened to give 'plant'.

Solution 3:

Etymonline suggests that it's a plant because it was planted:

The verb, "put in the ground to grow," is O.E. plantian, from L. plantare, from planta. Most extended usages are from the verbal sense. Sense of a building "planted" or begun for an industrial process is first attested 1789.

Solution 4:

George Washington Carver taught Henry Ford how to mass produce automobiles from a theory he developed by studying plants. The idea of an assembly line came from plants. Hence the term "plant".