The Old English word Æþeling means 'child of a noble family' - prince, in effect. Modern historians often use the term 'throne-worthy' to refer to those athelings of the royal house who were eligible for kingship. There was no automatic rule of primogeniture - a king's successor did not need to be his eldest son, and indeed was not necessarily his son at all. Thus, in the 9th century, King Athelwulf had five sons, four of whom became king in turn: Athelstan (d.