1873, an irregular shortening of rotator, originally in mathematics. Mechanical sense of "rotating part of a motor" is attested by 1903; specifically of helicopters from 1930.
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."
in helipad, heliport, etc., a modern word-forming element meaning "helicopter," abstracted ignorantly from helicopter (q.v.), which is properly helico- + -pter.