the craft or practice of metalworking; the work of a blacksmith.
From 'ad-' (to, toward) combined with 'smithing' (the craft of a smith/blacksmith). This appears to be a rare or archaic variant emphasizing the directed, purposeful nature of the metalworking craft.
This might be one of the rarest words in English—it barely appears in historical records, suggesting it was either a very local usage or a writer's one-time invention that never caught on, unlike 'smithing' which became standard.
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