Overview
Ahasuerus ( ; , commonly Achashverosh; , in the Septuagint; in the Vulgate) is a name applied in the Hebrew Bible to three rulers and to a Babylonian official (or Median king) in the Book of Tobit. It is a transliteration of either Xerxes I or Artaxerxes; both are names of multiple Achaemenid dynasty Persian kings.
Etymology
The Hebrew form is believed to have derived from the Old Persian name of Xerxes I, Xšayāršā (< xšaya 'king' + aršan 'male' > 'king of all male; Hero among Kings'). That became Babylonian Aḥšiyâršu (, aḫ-ši-ia-ar-šu) and then Akšîwâršu (, ak-ši-i-wa6-ar-šu) and was borrowed into Hebrew as Ăḥašwêrôš and thence into Latin as Ahasuerus, the form traditionally used in English Bibles.
The Persian name was independently rendered in Ancient Greek as Xérxēs. Many newer English translations and paraphrases of the Bible have used the name Xerxes.
Book of Esther
"Ahasuerus" is given as the name of a king, the husband of Esther, in the Book of Esther. He is said to have “ruled over a hundred and twenty-seven provinces from India to Nubia" — that is, over the Achaemenid Empire. There is no reference to known historical events of the reign of Xerxes in the story; some consider the narrative of Esther was to provide an aetiology for Purim, and that the name Ahasuerus is usually understood to refer to a fictionalized Xerxes I, who ruled the Achaemenid Empire between 486 and 465 BCE. Outside of the book of Esther, history records that Xerxes was married to Amestris, not Vashti or Esther. Moreover, it is understood that Persian kings did not marry outside a restricted number of Persian noble families. In the Septuagint, the Book of Esther refers to the king as 'Artaxerxes,' who was the younger son of Xerxes.
From Wikipedia (CC BY-SA 4.0).