And when the wind gets going the division between "sea" and "atmosphere" gets pretty blurred here on earth.

Also, you seem to be operating under a misunderstanding about the derivation of "planet" - it has nothing to do with the derivation of "plane".

Planets are so called because they were points of light that 'wandered' in the sky - the word comes from the Greek for 'wanderer'.

Plane comes from the Latin for a plane (not to be confused with the plane tree which comes from the Greek for 'broad' via Latin).

So - they are not called "Plane-ettes" in the first place - they are "wandering stars".