Dr.Smith wrote:

I heard or read somewhere that the name 'Viper' is an unofficial name given
to the Falcon now by pilots who watched "Battlestar Galactica" as children,
or is it named DIRECTLY after snakes?

The beaurocrats took far too long to decide on a name, and the pilots
flying the so-far-unnamed fighter took to calling it "Viper", after the
fighters used by the good guys on the then-current show, Battlestar
Galactica. The F-16 with its sidestick, laid-back seat and fly-by-wire
seemed futuristic, and the name fitted.

It was eighteen months after the plane went into service that the
official name "Fighting Falcon" was bestowed.