Spider webs

[Julia Cherry]

Why are spider webs called cobwebs?

[Clanad]

 Cob is the old term for a spider, therefore, a cobweb is a spider web.   A cobweb is a single strand of dust, whereas spider webs are multi-stranded in a pattern. Cobweb does mean "spider web" in its earliest incarnations (14th century).  However, less than one hundred years later it was already being used to refer to similar material produced by insects (versus arachnids), and one hundred years after that, it referred to "any musty accumulation". 
The word is formed from cob "spider" and web.  Cob was originally coppe (as in Middle English coppeweb, 1323) and later cop.  It derived from Old English attercop "spider", which was formed from atter "poison" and coppe "head".  Coppe is thought by some to be related to cob "ear of corn" which would make a cob more a "head of corn".  We don't hear other uses of cob much here in the U.S., but in Britain it has other meanings: "nut" (shaped like a head), "horse" (has a large head) and "male swan" (chief or "head" swan) and a type of (head-shaped) "loaf".  Some think the links between these words tenuous, at best. (Source: Take Our Word For It)

[Tim Baxter]

Bit late now but we could have asked Tolkien who wrote a verse "Attercop, Attercop." and, later, even named his famously evil spider "Shelob" both derived from early/middle English.