Attercop is actually a word in English too, although really really antiquated. The only time I've seen it used is when Bilbo was taunting the spiders of Mirkwood in
The Hobbit.
The
OED (not
that OED) says that the English etymology is from Old English "attorcoppe", with "ator" meaning poison or venom, and "copp" meaning head, round, summit.
Cop also has some relation to the word spider in general, like in "
cobweb".