Calla, absolutely rare, of Reggio and Vibonese, should be due to a mistaken transcription of Callà, which is also typically Calabrian, of Mammola in the Reggio area and of Serra San Bruno in the Vibonese, and which could derive from an Italianization of the Greek surname Callas, or derive from nicknames based on the Greek adjective ????? kalòs (beautiful).
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