Mid 17th century; earliest use found in Robert Vilvain (d. 1663), physician and philanthropist. From classical Latin rēgifugium festival celebrated at Rome on 24 February, associated with the expulsion of the kings (recorded only in an 8th-cent. epitome of a 2nd-cent. grammarian, but also described in Ovid, who calls it rēgis fuga flight of the king (Fasti 2. 685)) from rēgi-, alternative stem of rēx king + fugere to flee + -ium.