http://www.etymonline.com/index.php?term=terrainQuote:
1727, "ground for training horses," from Fr. terrain "piece of earth, ground, land," from O.Fr. (12c.), from V.L. *terranum, from L. terrenum "land, ground," from neut. of terrenus "of earth, earthly," from terra "earth, land," lit. "dry land" (as opposed to "sea"); from PIE base *ters- "to dry" (cf. Skt. tarsayati "dries up," Avestan tarshu- "dry, solid," Gk. teresesthai "to become or be dry," L. torrere "dry up, parch," Goth. þaursus "dry, barren," O.H.G. thurri, Ger. dürr, O.E. þyrre "dry;" O.E. þurstig "thirsty"). Meaning "tract of country, considered with regard to its natural features" first attested 1766.
http://www.etymonline.com/index.php?term=lunarQuote:
"of or pertaining to the moon," 1626, from O.Fr. lunaire, from L. lunaris "of the moon," from luna "moon," (with capital L-) "moon goddess," from *leuksna- (cf. O.C.S. luna "moon," O.Pruss. lauxnos "stars," M.Ir. luan "light, moon"), from the same source as lux, lumen "light." The luna moth (1884) so called for the crescent-shaped markings on its wings.
http://www.etymonline.com/index.php?term=SolQuote:
"the sun," c.1450, from L. sol "the sun," from PIE *s(e)wol-, from base *saewel- "to shine, the sun" (cf. Skt. suryah, Avestan hvar "sun, light, heavens;" Gk. helios; Lith. saule; O.C.S. slunice; Goth. sauil, O.E. sol "sun," swegl "sky, heavens, the sun;" Welsh haul, O.Cornish heuul, Breton heol "sun;" O.Ir. suil "eye"). The PIE element -*el- in the root originally was a suffix and had an alternative form -*en-, yielding *s(u)wen-, source of Eng. sun (q.v.).