helix n.

Proto-Indo-European root meaning "to turn, revolve," with derivatives referring to curved, enclosing objects.

It forms all or part of: archivolt; circumvolve; convoluted; convolution; devolve; elytra; evolution; evolve; Helicon; helicopter; helix; helminth; lorimer; ileus; involve; revolt; revolution; revolve; valve; vault (v.1) "jump or leap over;" vault (n.1) "arched roof or ceiling;" volte-face; voluble; volume; voluminous; volute; volvox; volvulus; vulva; wale; walk; wallet; wallow; waltz; well (v.) "to spring, rise, gush;" welter; whelk; willow.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit valate "turns round," ulvam "womb, vulva;" Lithuanian valtis "twine, net," vilnis "wave," apvalus "round;" Old Church Slavonic valiti "roll, welter," vlŭna "wave;" Greek eluein "to roll round, wind, enwrap," eilein "twist, turn, squeeze; revolve, rotate," helix "spiral object;" Latin volvere "to turn, twist;" Gothic walwjan "to roll;" Old English wealwian "roll," weoloc "whelk, spiral-shelled mollusk;" Old High German walzan "to roll, waltz;" Old Irish fulumain "rolling;" Welsh olwyn "wheel."

"spiral-shaped," c. 1600, from Latin helicem (nominative helix) "spiral" (see helix) + -al (1).

1861, from French hélicoptère "device for enabling airplanes to rise perpendicularly," thus "flying machine propelled by screws." From a Latinized combining form of Greek helix (genitive helikos) "spiral" (see helix) + pteron "wing" (from PIE root *pet- "to rush, to fly").

The idea was to gain lift from spiral aerofoils, and it didn't work. Used by Jules Verne and the Wright Brothers, the word was transferred to helicopters in the modern sense by 1918 when those began to be developed. Nativized in Flemish as wentelwiek "with rotary vanes."