Sword of the Morning is a title right? Doesn't really count as a nickname. That'd be like saying your favorite nickname was Hand of the King.
No its not a title. No other Dayne has been called that nor anyone else. That's like saying the Blackfish is a title
incorrect. whoever bears Dawn is called the Sword of the Morning. Arthur Dayne is just the last at this point.
I don't exactly remember where it was in the books. it could have come from a So Spake Martin or something on Westeros.
I haven't read them yet, but I either read or heard something about a SotM being in the Dunk and Egg series.
I don't recall. and I read them all for the second time recently. edit: just checked the wiki because I was curious and Ulrick Dayne, a past Sword of the Morning, is apparently referenced at some point.