Attercop: “The word is Old English, from attor, poison + cop, the head. (Cop, or coppa, was also used by itself to mean a spider, so cobweb ought really to be spelled copweb.) The name was given to spiders in the mistaken belief that they were all poisonous to humans. By the sixteenth century it had begun to be applied to a cross-grained, ill-natured, figuratively venomous person.”
Word and monster well-matched, with echoes of Professor Tolkien as well.