More covered with cobwebs or resembling cobwebs than something else; comparative form of cobwebby.
From 'cobweb' (from Middle English 'coppewebbe', originally 'spider web') plus the comparative suffix '-er'. The word evolved from folk etymology where people thought 'cop' meant spider, though it likely came from Middle Dutch 'coppe' (head/cup shape of spider body).
The shift from 'coppewebbe' to 'cobweb' shows how people reshape unfamiliar words to match known ones—'cop' sounded like a spider part to English speakers, so they reinterpreted it, similar to how 'hamburger' became associated with ham instead of Hamburg!
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