In a state of winning or triumph; winning or victorious (archaic).
From 'a-' plus 'win.' This follows the Old English pattern of forming state-of-being adverbs by prefixing 'a-' to verbs, creating a snapshot of the action.
The 'a-' prefix was especially useful for verbs because it let speakers freeze a moment in time—'awin' suggests not just winning but being in the state of victory!
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