Festus says the Romans called victims wholly consumed by fire prodigæ hostiæ (victims prodigalised), and adds that those who waste their substance are therefore called prodigals. This derivation can hardly be considered correct. Prodigal is pro-ago or prod-igo (to drive forth), and persons who had spent all their patrimony were “driven forth” to be sold as slaves to their creditors.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
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