One of the mysteries of the English language finally explained.
1English regional (northern) and Scottish. Any of various (chiefly black-billed) birds; especially the carrion crow, Corvus corone. Now historical.
2Scottish depreciative. A blackleg, a strike-breaker; = "blacknob". Now historical.
Early 19th century (in an earlier sense). From black + neb. The motivation for senses 1 and 3 is unclear; sense 3 could either (in spite of the apparent chronology) show an alteration of blacknob by association with sense 2, or could perhaps show an extended use of sense 2, the strike-breaker being compared to a carrion crow.
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