- plane (n.1)
- "flat surface," c. 1600, from Latin planum "flat surface, plane, level, plain," noun use of neuter of adjective planus "flat, level, even, plain, clear," from PIE *pla-no- (source also of Lithuanian plonas "thin;" Celtic *lanon "plain;" perhaps also Greek pelanos "sacrificial cake, a mixture offered to the gods, offering (of meal, honey, and oil) poured or spread"), suffixed form of root *pele- (2) "to spread out; broad, flat" (source also of Old Church Slavonic polje "flat land, field," Russian polyi "open;" Old English and Old High German feld, Middle Dutch veld "field"). Introduced (perhaps by influence of French plan in this sense) to differentiate the geometrical senses from plain, which in mid-16c. English also meant "geometric plane." Figurative sense is attested from 1850. As an adjective from 1660s.
- plane (n.2)
- 1908, short for aeroplane (see airplane).
- plane (n.3)
- "tool for smoothing surfaces," mid-14c., from Old French plane, earlier plaine (14c.), from Late Latin plana, back-formation from planare "make level," from Latin planus "level, flat" (see plane (n.1)).
- plane (n.4)
- "tree of the genus Platanus," late 14c., from Old French plane, earlier plasne (14c.), from Latin platanus, from Greek platanos, earlier platanistos "plane tree," a species from Asia Minor, associated with platys "broad" (see plaice (n.)), in reference to its leaves. Applied since 1778 in Scotland and northern England to the sycamore, whose leaves somewhat resemble those of the true plane tree.
- plane (v.1)
- "to make smooth," early 14c., "to gloss over, explain away;" mid-14c. as "to make smooth or even," from Old French planer "to smooth, level off; wipe away, erase" (12c.), from Late Latin planare "make level," from Latin planus "level, flat" (see plane (n.1)). In early use in English often plain. Related: Planed; planing.
- plane (v.2)
- "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" (see plane (n.1)), 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.
