helicopter (n.)
1861, from French hélicoptère "device for enabling airplanes to rise perpendicularly," thus "flying machine propelled by screws." From Greek helix (genitive helikos) "spiral" (see helix) + pteron "wing" (see ptero-).

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 when those were developed in the 1920s. Nativized in Flemish as wentelwiek "with rotary vanes."