An archaic word meaning at or to a height; positioned high up or at an elevated position.
From Old English 'a-' (at, in) plus 'height,' following the same pattern as other Old English locational adverbs. This construction was common from Old through Early Modern English.
English used to be much more willing to add prefixes to describe positions and states. 'Aheight' was clear and efficient—one word told you something was positioned up high. We mostly lost these constructions, relying instead on full phrases like 'at a height.'
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