I've spent over a year now telling you all about the events that led up to you listening to your radio. Where tubes, transistors, DJs, formats and all manner of things radio originate. I realized only this morning I had not yet discussed the origin of the word radio itself.
It has many definitions, so I will dryly begin there:
ra·di·o (rd-)n. pl. ra·di·os
1. The wireless transmission through space of electromagnetic waves in the approximate frequency range from 10 kilohertz to 300,000 megahertz.
2. Communication of audible signals encoded in electromagnetic waves.
3. Transmission of programs for the public by radio broadcast.
4. An apparatus used to transmit radio signals; a transmitter.
-An apparatus used to receive radio signals; a receiver.
-A complex of equipment capable of transmitting and receiving radio signals.
-A station for radio transmitting.
-A radio broadcasting organization or network of affiliated organizations.
5. The radio broadcasting industry.
6. A message sent by radio.
The word radio isn't much older than radio itself. It began to appear in 1907, abstracted from earlier combinations using the word such as radiophone (1881) and radio-telegraphy (1898). These words were only marginally older, and themselves originate with the liberal use of the prefix "rad" from the word radiation.
The root word Radiation is much older, coming into common use in 1555 as an Anglo adaptation of the Greek verb radiare , meaning "to shine or beam." That word comes from The earlier Latin Radius, meaning "staff, spoke of a wheel, beam of light." Its origin is unknown but may be the older Latin word radix meaning root. Possibly the Sanskrit word vardhate "rises, makes grow," or the ancient Greek ardis meaning "sharp point."
*The term Wireless dates back only to 1894 beginning as a direct reference to the lack of a telegraph wire. By 1903 it was being used to refer to radio, and radios.
The first use of the word radio to mean "radio-receiver" was only in 1917, and its use meaning "broadcasting medium" only in 1922! Prior to that the term Wireless remained far more dominant. It was not until WWII that the military's preference for the word radio over wireless changed the preference.
So that's it. Radio begins as a reference to wheel spokes and now has nothing to do with wheels spokes, beams of light, or sharp points... except for car radios, fiber optics routers, and .. dang I cant think of a pointy thing.