I prefer to consult the natural world for things like this. Animals, insects and plants are ace for being named after what they look like (grasshopper, daddy long-legs, slug, orange cone flower, lamb's foot etc) which can really help you out if you know what kind of feeling your monster is supposed to invoke.
Your monster look like a spider? Call it a huntsman or a prowler. Is it white? Paper prowler. Is it silver? Gray huntsman or ash weaver. That's how I tend to do it, but then I really like simplicity in world building and names. I think it's the reason why worlds like the one in Harry Potter are so quick to swallow you up-- it's easy to become immersed in a world built on simple concepts. Things are easy to remember if they make sense.
Then again, if you place a lot of value in being 100% unique and original then maybe you're better combining well known names and terms into new ones that sound like you need them to.
Killer whale + oxen = Killox.
Dreadful + skinny + sallow = Skindresal.
I dunno, play around, but there are cool combinations out there that may work for you.