Radar is a word built to be read aloud, and it is also a palindrome by accident.
Radar began as an acronym: RAdio Detection And Ranging. Etymonline and Merriam-Webster both date it to 1941, and Etymonline calls it an acronym "more or less," since it is stitched together from pieces of the phrase rather than only initials. Those dates are the first known uses in print.
The Navy itself used the word earlier. Wikipedia says the United States Navy coined it in 1940, and Howeth's 1963 History of Communications-Electronics in the United States Navy credits two naval officers, Furth and Tucker, with the coinage. Howeth says the Chief of Naval Operations directed in November 1940 that the word be used as an unclassified term for the then-secret project. Sources differ on the officers' initials and the exact day, so the safe version is that the Navy coined it in November 1940 and print records begin in 1941.
The word named something older. NPR says Heinrich Hertz showed in the late 19th century that radio waves reflect off metal. It also says Christian Hülsmeyer patented the Telemobiloskop in 1904, a device with a transmitter and receiver meant to help ships avoid collisions. The technology existed decades before anyone had a short name for it.
The name had competition. Etymonline says the American term won out over the British radiolocation. In practice that meant a US Navy label became the standard word in English and, as Wikipedia notes, in other languages.
Then the capitals fell away. Wikipedia says the word has lost all capitalization as it became a common noun, which is why the spelled-out phrase now feels like a historical footnote.
The word kept spawning copies. Etymonline lists sonar in 1946, a contraction of "sound navigation ranging" modeled on radar. It also records a figurative use from 1950, and gaydar by 1992.