A propeller is defined as "a device having a revolving hub with radiating blades, for propelling an airplane, ship, etc.", whereas a rotor can refer to many, many disparate things, contained within electric motors to gyros.
How did the helicopter come to have the word "rotor" applied, rather than "propeller"?
The earliest reference to "helicopter rotor" in the aviation press I could find was this article dated 1915.
https://www.flightglobal.com/pdfarch...0-%200266.html
Esoteric I know, and only anorak wearers would be interested.
