Etymology of the word *plane* as used in *airplane/aeroplane*

I was curious about this etymology since plane retains a distinct meaning that only applies to airplanes whereas other words like aircraft, airship, airliner, air-vessel, air-boat, aeromotive, etc. all have meanings of the non-air (or aero) part of these words/phrases that are more generic.

Wikipedia is uncertain if the word is derived from Latin or Greek:

comes from the Greek ἀήρ (aēr), "air" and either Latin planus, "level", or Greek πλάνος (planos), "wandering".

Wiki's sources for Latin are Merriam-Webster Dictionary, and for Greek are both Oxford Dictionaries and A Greek-English Lexicon.

Dictionary.com cites the 2017 Random House's entry with the opinion that plane may be from the sculptural aspect of the aircraft as a relative flat thing similar to forme plane:

1870-75; < French aéroplane, equivalent to aéro- aero- + -plane, apparently feminine of plan flat, level (< Latin plānus; cf. plain), perhaps by association with forme plane; apparently coined and first used by French sculptor and inventor Joseph Pline in 1855

The 2017 Online Etymology Dictionary by Douglas-Harper argues that there was a pre-existing meaning of any heavier-than-air flat thing (like Beetles' wings) to be called planes:

1866, originally in reference to surfaces such as shell casings of beetle wings, from French aéroplane (1855), from Greek-derived aero- "air" (see air (n.1)) + stem of French planer "to soar," from Latin planus "level, flat" (from PIE root *pele- "flat; to spread"). Later extended to the wing of a flying machine. Meaning "heavier than air flying machine" is first attested 1873 and probably is an independent coinage in English.

But the entry then adds the comparison to the Greek almost as a way of sort of hedging it's bet:

Greek aeroplanos meant "wandering in the air," from planos "wandering" (see planet).

I also found this explanation attributed the American-Heritage Dictionary:

plane in the sense of “winged vehicle,” first recorded in April 1908, is a shortened form of aeroplane. In June of that year plane appeared in a quotation from the London Times that mentioned one of the Wright brothers. Aeroplane, first recorded in 1866, is made up of the prefix aero-, “air, aviation,” and the word plane, referring to the structure designed to keep an air vehicle aloft. Originally the plane in such contexts was imagined as flat, hence the choice of the word plane; in practice this surface must curve slightly in order to work. The word aeroplane for the vehicle is first found in 1873. The first recorded appearance of the form airplane in our current sense, which uses air- instead of aero-, is found in 1907. An American flies in an airplane while a Briton still travels in an aeroplane, but both can catch a plane.

From all of these, I see three distinct theories evolving for the word plane as it is used in airplane/aeroplane:

1. Plane, like planet, is derived primarily from the the Greek word planos meaning wandering (per Wikipedia quoting Oxford Dictionaries and A Greek-English Lexicon; also alluded to by Online Etymology Dictionary)
2. Plane, like plain is derived primarily from the Latin plānus and the primary feature is the sculptural features of the wings being flat and level as in forme plane (per Wikipedia quoting Merriam-Webster Dictionary; per Random House Dictionary; per the attribution to American-Heritage Dictionary)
3. Plane is derived primarily from the French planer meaning to soar (per primary theory given by Online Etymology Dictionary)

Anyone able to clear this mess up?

Solution 1:

It all started with the term aeroplane later replaced by the more common airplane. The origin of plane is from the root "pele-" (flat, to spread) from which the Latin "planum":

• 1866, originally in reference to surfaces such as shell casings of beetle wings, from French aéroplane (1855), from Greek-derived aero- "air" (see air (n.1)) + stem of French planer "to soar," from Latin planus "level, flat" (from PIE root pele- (2) "flat; to spread"). Later extended to the wing of a flying machine. Meaning "heavier than air flying machine" is first attested 1873 and probably is an independent coinage in English. Also see airplane. Greek aeroplanos meant "wandering in the air," from planos "wandering".

Airplane (n.)

• 1907, air-plane, from air (n.1) + plane (n.1); though the earliest uses are British, the word caught on in American English, where it largely superseded earlier aeroplane (1873 in this sense and still common in British English).

Plane:

• "soar, glide on motionless wings," early 15c., from Old French planer "to hover (as a bird), to lie flat," from plan (n.) "plane," from Latin planum "flat surface" (root pele- (2) "flat; to spread"), on notion of bird gliding with flattened wings. Of boats, etc., "to skim over the surface of water," it is first found 1913. Related: Planed; planing.

pelə-:

Proto-Indo-European root meaning "flat; to spread."

• It forms all or part of: airplane; dysplasia; ectoplasm; effleurage; esplanade; explain; explanation; feldspar;

(Etymonline)

Solution 2:

I always thought that its derivation was from the geometric term plane

Plane [pleyn]/ noun

1. a flat or level surface.
2. Geometry. a surface generated by a straight line moving at a constant velocity with respect to a fixed point.
3. Fine Arts. an area of a two-dimensional surface having determinate extension and spatial direction or position.

As an airplane moves, there is a plane of air that moves below the wings, allowing for lift. If you consider the wings to be the line, you can see how the geometric definition above (definition #2) aptly describes what it occurring. Similarly, a hydroplaning car experiences the same effect where a thin layer of water creates a frictionless plane below the tires.

Solution 3:

It surprised me just now that “airplane” is a puzzle in etymology. The air part is trivial, but surely plane is or ought to be a reference, its original logic now perhaps permanently lost, to the wings. A gyrocopter is not a plane. Curiosity over the difference in origin between the terms airship and airplane led me to this discussion. Airship is a fine coinage, for both airships and water-going ships depend on buoyancy (never mind rocket ships!). So by retro-logic, to entertain and put things as they should be rather than truly are, “plane” is focussed on the wings and perhaps the engine system to drive them onward.