An archaic or dialectal word meaning in a heap; piled up or accumulated together in a mass.
From Old English construction 'a-' (in, on) combined with 'heap.' This prefix construction was standard in Middle English but has largely disappeared from modern English.
When you see 'aheap,' 'afire,' 'asleep'—you're looking at an old English prefix that basically meant 'in a state of.' It's like the linguistic equivalent of watching a species evolve; these constructions worked great for centuries, then got replaced and mostly went extinct.
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