Adam Clarke, on Esth 9:26

“And since that time these days are called Phurim, that is, of lots: because Phur, that is, the lot, was cast into the urn. And all things that were done, are contained in the volume of this epistle, that is, of this book:”

“They called these days Purim - That is from pari, the lot; because, as we have seen, Haman cast lots to find what month, and what day of the month, would be the most favorable for the accomplishment of his bloody designs against the Jews. See on Est 3:7 (note). And of that which they had seen - The first letter to which this second refers, must be that sent by Mordecai himself. See Est 9:20.”

Imported from an open dataset — not yet checked against the printed edition.