A young goat; a kid goat.
From 'goat' + '-ling' (Old English diminutive suffix meaning 'small' or 'young'). The '-ling' suffix appears in 'duckling', 'gosling', etc.
The '-ling' suffix is shrinking in modern English—we barely use it anymore, but 'goatling', 'gosling', and 'duckling' are relics of when we regularly made diminutives this way for young animals!
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