I think they have similarities. In both cases it is something/someone that are very close to humans, but still not totally the same. Totally different is less scary, I wanted to say like who is scared of a tree, but many people are, but again, mainly in the cases they look like actual being, seeming to have faces mouths and crooked hands. So again, as soon as something seems alive, but isnt it can freak people out and people are also freaked out if they don't understand the behaviour ( why is it doing that... that is not a normal reaction in this situation..)
An old name for spider was atorcoppe or attercop. meaning pusshead or poisonhead. Though I see the connection with adder, poisonous snake aswell, so you could perhaps consider it as adderhead. (and just found out welsh calls it pryf copyn)
In Danish and Norwegian a spider is still called edderkop(p).
The current word for spider, comes from weaver/spinner, it spins a web
In middleschool they showed us the movie "the Wave" that has definitely left an impression