cobweb (n.)

"spider," Middle English atter-coppe, from Old English atorcoppe "spider," literally "poison-head," from ator "poison, venom" (Middle English atter), from Proto-Germanic *aitra- "poisonous ulcer" (source also of Old Norse eitr, Old High German eitar "poison;" German eiter "pus," Old High German eiz "abscess, boil;" Old English atorcræft "art of poisoning") + copp "top, summit, round head," probably also "spider" (compare cobweb and Dutch spinne-cop "spider").

Amptes & attircoppes & suche oþer þat ben euere bisy ben maide to schewe man ensaumple of stodye & labour. [Elucidarium of Honorius of Autun (Wycliffite version) c. 1400]

Archaic and provincial; used 20c. by Tolkien. It also lingered in Northern England dialect in the sense "peevish, ill-natured person" (c. 1500).

a word or set of identical words with a wide range of meanings, many seeming to derive from notions of "heap, lump, rounded object," also "head," and metaphoric extensions of both. With its cognates in other Germanic languages, of uncertain origin and development.

"The N.E.D. recognizes eight nouns cob, with numerous sub-groups. Like other monosyllables common in the dial[ect] its hist[ory] is inextricable" [Weekley]. In the 2nd print edition, the number stands at 11. Some senses are probably from Old English copp "top, head," others probably from Old Norse kubbi or Low German, all the words perhaps trace to a Proto-Germanic base *kubb- "something rounded."

Among the earliest attested English senses are "headman, chief," and "male swan," both early 15c., but the surname Cobb (1066) suggests Old English used a form of the word as a nickname for "big, leading man." The "corn shoot" sense is attested by 1680s.