pelagic
"pertaining to the sea," 1650s, from L. pelagicus, from Gk. pelagikos, from pelagos "sea," from PIE *p(e)lag- "to spread out" (cf. Gk. plagos "side," L. plaga "hunting net, curtain, region"), from base *pele- "spread out, flat" (see plane (1)).
plane (1) "flat surface," c.1600, from L. plantum "flat surface," properly neut. of adj. planus "flat, level, plain, clear," from PIE *pla-no- (cf. Lith. plonas "thin;" Celtic *lanon "plain;" perhaps also Gk. pelanos "sacrificial cake, a mixture offered to the gods, offering (of meal, honey, and oil) poured or spread"), suffixed form of base *pele- "to spread out, broad, flat" (cf. O.C.S. polje "flat land, field," Rus. polyi "open;" O.E., O.H.G. feld, M.Du. veld "field"). Figurative sense is attested from 1850. The verb meaning "soar, glide on motionless wings" is first recorded 1610s, from M.Fr. planer (16c.), from L. planum on notion of bird gliding with flattened wings. Of boats, etc., "to skim over the surface of water" it is first found 1913.
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