No, I believe it's just a colloquial term bandied about by anthropomorphic aficionados since the days of BBS services and photocopied fanzines. Alas, due to sensationalistic journalism, the term has gained notoriety in the general population. Er, "kaiju" isn't a registered name, is it? It's just a word describing the legion of titanic reptiles and other beasties practicing urban renewal in Japan, right? If so, the terms are relative.

Tempt the Hand of Fate and it'll give you the "finger"!