The present participle of commerce (archaic/rare); engaging in trade or business transactions.
From commerce (Latin commercium, 'trade, merchandise') + -ing. This is an archaic usage; 'commerce' as a verb has been largely replaced by more specific terms like 'trade' or 'do business'.
The word 'commercing' reveals how thoroughly English speakers have shifted from thinking of commerce as an active verb to treating it as purely a noun — language reflects what societies actually do.
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