This good Old and Middle English word was used from the mid 1930s onward, which is a bit like being handed one’s own silver platter for collateral.  But!  We learn from Google’s Ngram viewer that it was also used from the mid 1800s right up to before publication of The Hobbit.  Most of those references seem to be dictionaries – philological attempts to gather rustic spoken words as the Grimms did, but also in the occasional written work.  The word survives as a fragment “cob” in “cobweb”

• 08.096 Attercop! Attercop!
• 08.097 Attercop! Attercop!
• 08.098 no spider has ever liked being called Attercop,
• 08.119 and ‘Attercop’ from among the trees away on the right.
• 08.119 ‘Attercop’ made them so angry

Update 2015.06.08: since no spider has ever liked being called it, I am considering it an insult and tagging it “low”.

Tolkien, J.R.R. The Annotated Hobbit.  Revised and expanded edition annotated by Douglas A. Anderson. Houghton Mifflin Company. Boston. Print.