A young buck (male deer), or a dialectal/archaic term for a young male animal.
From Middle English and dialectal English, derived from 'buck' (male deer) with the diminutive suffix -erel, indicating a young or small buck.
Bockerel is an archaic diminutive that reveals how English once had more -erel suffixes for 'small versions'—we still use it in scoundrel, but it's dying out elsewhere.
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