The Answer
The French words hélico (from the Greek helix, meaning spiral) and ptère (from the Greek pteron, meaning wing).
It’s commonly assumed that the the word helicopter was formed by combining heli with copter. We even use each part and prefixes and suffixes of other words like helipad and quadcopter.
In fact, the word helicopter comes from the French word hélicoptère. The roots of this word are hélico and ptère.
helicopter (n.)
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 Greek word pteron also forms part of the words pterosaur (from Greek pteron and sauros, meaning “wing lizard”), pterodactyl (Greek for “wing finger”) and pteranodon (“wing toothless”).
I think it’s time that we start using the original parts in those other words – helicopad and quadpter (maybe quapter?)
Better yet I think it’s time to start treating the p in helicopter as silent as it is in pterodactyl.