(archaic or poetic) Some time ago; beforehand; formerly.
She runs you through, nor asks the word.
O thou, that dear and happy Isle,
The garden of the world erewhile,
Thou Paradise of the four seas
Which Heaven planted us to please,
The dame sans merci's broken strain,
Whom I erewhile, perchance, have known,
When Orleans filled the Bourbon throne,
A siren singing by the Seine.