The narrator of the song is a man who was jilted by his lover. Although dealing with the paradoxes he sees himself posed to in a very subtle and poetic manner, this was a folk song and not written by nobles. The courtly ideal of romantic love in the middle ages, practised by knights and noblemen, was loving a lady and adoring her from a distance, in a very detached manner. There was hardly a dream and sometimes not even a wish that such love could ever be answered.
As a version of the song exists which is set in Whittington Fair and which is presumed to be equally old, it is puzzling why the lieu d'action of the song eventually became reverted to Scarborough. A possible explanation is that this is a hint from the singer to his lover, telling how she went away suddenly without warning or reason. Scarborough was known as a town where suspected thieves or other criminals were quickly dealt with and hung on a tree or à la lanterne after some form of street justice. This is why a 'Scarborough warning' still means 'without any warning' in today's English. This would also account for the absence of any suggestion of a reason for her departure, which could mean either that the singer doesn't have a clue why his lady left, or perhaps that these reasons are too difficult to explain and he gently leaves them out.
The writer goes on to assign his true love impossible tasks, to try and explain to her that love sometimes requires doing things which seem downright impossible on the face of it. The singer is asking his love to do the impossible, and then come back to him and ask for his hand. This is a highly unusual suggestion, because in those days it was a grave faux-pas to people from all walks of life for a lady to ask for a man's hand. Yet it fits in well with the rest of the lyrics, as nothing seems to be impossible in the song.
把大鼻子給震了吧啊~