“Cobweb” is probably the source of the rare word “cob”, which means “spider”.  The root of that syllable is “cop”, to grab or capture.

• 08.003 The nastiest things they saw were the cobwebs:
• 08.003 dark dense cobwebs with threads extraordinarily thick,
• 08.101 in your cobwebs crazy.

“† cob, n.4.” OED Online. Oxford University Press, September 2015. Web. 4 October 2015.