First, I do not think we have textbook definition of "drone" as such words change meaning based on what technologies are actually available, but quite a lot of technical terms come from or are inspired by science fiction. While I did not read lots of science fiction and most of that was not in English, I think "drone" for a long time used to mean something like "mobile robot capable of
autonomously performing a series of tasks", mostly in contexts of mining, cargo transportation and reconnaissance.
Airborne association with drones is quite a recent thing with rise of "military drones" (mostly recon) and subsequently manufacturers of RC multirotors using a word distancing their products from RC toys. RC multirotors are drones only in the sense that they maintain altitude and orientation autonomously.