If it is as simple as OYF's nickname (West Venom/Poison), it might be understandable, because OYF used poison a lot and he came from the west border. However, sometimes nickname is not so obvious, like for example Tian Boguang's nickname is Ten Thousand Miles Loner. Who came up with the phrase "ten thousand"? Why not "a thousand"? Also, like those long and complicated nicknames of the Four Evils in DGSD, who came up with those? Mostly the one having the nickname would say that his/her nickname was given to him/her by people in the martial world. If so, how did people in the martial world agree on the nickname (since people are bound to have their own preference/opinion)? If the nickname is self-made by the person having it, wouldn't that be kind of chest-thumbing him/herself?