In mining, the space left behind after coal or ore has been extracted from a mine.
From Middle English or possibly Welsh origin, 'goaf' entered mining terminology to describe the empty cavity left by extraction. The word became standard technical jargon in British mining regions.
Mining created its own vocabulary, and 'goaf' is a perfect example—coal miners needed a specific word for the empty spaces underground, just like different industries develop their own secret languages.
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