Sword of the Morning
From A Wiki of Ice and Fire
The Sword of the Morning is a title of House Dayne bestowed on the knight who bears their ancestral greatsword Dawn. The Sword of the Morning is always a member of House Dayne.  The title is not necessarily passed to the lord of the house, but to the knight considered most worthy to wield it, as decided within the House.   If there is no Dayne knight considered worthy, the title lies dormant; the last to bear the title was Ser Arthur Dayne, a famed knight of the Kingsguard.