Originally Posted by
Ascend Charlie
I tried to find the origins but failed - by memory it is F for fighter, two syllables for jet powered, similarly Bear is a bomber but not jet-powered.
You are on the right track, two syllables for jets, but BEAR is single syllable, therefore prop.
Also these are often incorrectly referred to (even by Wiki, who would have thought?) as NATO names.
Althought they are used by NATO, the names come from the ATIE tech group, then approved by the ASCC standards body.
In the late 1990s this process was given the flick as the designators of Russian and Chinese aircraft were well known, and therefore no need for codenames.
Accordingly, the J-10 received no name, nor have others since.
So I would be surprised if this "FAGIN" tag has officially been allocated to the J-20.