plan

First recorded in 1670–80; from French: “ground, plan, groundwork, scheme,” noun use of the adjective: “flat” (see plane¹), a learned borrowing of Latin plānus “level” (cf. plain¹)

1. Plan, project, design, scheme imply a formulated method of doing something. Plan refers to any method of thinking out acts and purposes beforehand: What are your plans for today? A project is a proposed or tentative plan, often elaborate or extensive: an irrigation project. Design suggests art, dexterity, or craft (sometimes evil and selfish) in the elaboration or execution of a plan, and often tends to emphasize the purpose in view: a misunderstanding brought about by design. A scheme is apt to be either a speculative, possibly impracticable, plan, or a selfish or dishonest one: a scheme to swindle someone.

The English noun plan comes from the French noun plan “a sketch, diagram, drawing, ground plan, plane surface,” from the adjective plan “flat, even, plane (in geometry).” French plan is a Latinized form of plain (with the same meanings), from the Latin adjective plānus “flat, level, horizontal, two-dimensional, plane (in geometry).” The French noun plan is also partly an alteration of the earlier French noun plant, a derivative of the verb planter “to plant, drive in, stick in, fix in place,” from Latin plantāre “to set in place, fix in place, plant, transplant.”
The meaning “an organized proposal or scheme of action” first appeared in 1635; the more etymological meaning “a drawing or diagram of an object made by projection on a horizontal plane” appeared in 1664.
The earliest citation for “a formal program for specified benefits” is first recorded in 1912, with specific reference to a savings plan.