Dugu Qiubai - what a mysterious fellow.
During his own time, he was supposed to be undefeated, so his name should have been famous. 100 years after his time, no one mentioned him. 200 years after his time, everyone probably forgot about him. About 400 years after his time into SPW, he was known by at least one person. A couple of more hundred years pass by, Shaolin elder Chengguan/Dengguan thought: "I heard that in a previous dynasty, there existed a swordsman called Dugu Qiubai..." Any theories for how his name was still known to the Qing dynasty Shaolin expert?
My theory is that by destiny, at least one person in each dynasty will rediscover Dugu Qiubai. Or, it could simply be the case that Linghu Chong/Feng Qingyang spread Dugu Qiubai's reputation after SPW.