“Chittering” is what the subtitles for Alien: Earth and The Watchers call the scary monster sounds that are kind of a cross between a creaking door and a really slow frog’s croak. When and where was it decided this was the sound fictional reptilian/insectoid creatures would make? And is there anything in actual nature that sounds like that.
Here’s a sample from Predator
(video of Peter Cullen describing coming up with and recording the iconic predator sound)