Note: E-NED notes that 'ATTERCOP' is misapplied to a spider's web.
ED-EDD has it as a valid meaning, with examples.
also in forms: ADDIRCOP, ADDURCOP, AFTERCROP, ATTERCAP, ATTERCOB, ATTERCOPPE, ATTERCROP, ATTORCOP, ATTORCOPPA, ATTURCOPPE, ATTYRCOPE, ATTYRCOPPE, EDDERCROP, EDTHERCROP, ETHERCAP, ETTERCAP, NATTERCROP, OTTERCOP
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Old English attorcoppa, from átor, attor, poison + coppa, derivative of cop top, summit, round head, or copp cup, vessel;
in reference to the supposed venomous properties of spiders
Cf. also Du.spinne-cop ‘spider,’ and cob-web, formerly cop-webbe; whence it appears probable that the simple coppa was itself = ‘spider'
From The Eclectic Review, Volume III, Part 1, 1807
Boucher's Supplement to Dr. Johnson's Dictionary