These beings are spies and they do not have a solid form so my train of thought is they are beings of pure knowledge (whether they shed their "mortal forms" long ago is a possibility). It is knowledge and the power it inherently holds that encompasses their society, culture, and race - making espionage and research critical components. With that in mind, I came up with a couple ideas, ultimately resulting in:

"Knomos"

Trying to harken some Greek knowledge and word-play here. So the words I was trying to use were "Kosmos" for "form" and "gnosis" for "knowledge". 

Edit: In advance, please forgive my knowledge and application of the Greek language.

I'm really digging this one, it's easy to pronounce, doesn't involve obscure languages, and yet sounds alien enough that we don't immediately associate it with earthling cultures.