"turning toward the moon," 1883, from seleno-, combining form from Selene "moon," + -tropic, from Greek tropos "a turning," from trepein "to turn" (from PIE root *trep- "to turn"). Related: Selenotropism.
a name of the moon goddess, equivalent to Latin Luna, from Greek selēnē "the moon; name of the moon goddess," related to selas "light, brightness, bright flame, flash of an eye." This is reconstructed to be from PIE root *swel- (2) "to shine, beam" (source also of Sanskrit svargah "heaven," Lithuanian svilti "to singe," Old English swelan "to be burnt up," Middle Low German swelan "to smolder") and to be related to swelter and sultry.
Daughter of Hyperion and Theia, sister of Helios. Related: Selenian "of or pertaining to the moon as a world and its supposed inhabitants," 1660s. Another early word for "moon-man, supposed inhabitant of the moon" is selenite (1640s); Greek had selēnitai "moon-dwellers, the men in the moon" (Lucian).
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit trapate "is ashamed, confused," properly "turns away in shame;" Greek trepein "to turn," tropos "a turn, direction, course," trope "a turning;" Latin trepit "he turns."
<a href="https://www.etymonline.com/word/selenotropic">Etymology of selenotropic by etymonline</a>
Harper, D. (n.d.). Etymology of selenotropic. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/selenotropic