Barber's poleThe origin of the red and white barber pole is associated with the service of bloodletting and was historically a representation of bloody bandages wrapped around a pole.[2] During medieval times, barbers performed surgery on customers, as well as tooth extractions. The original pole had a brass wash basin at the top (representing the vessel in which leeches were kept) and bottom (representing the basin that received the blood). The pole itself represents the staff that the patient gripped during the procedure to encourage blood flow.
from http://en.wikipedia.org/wiki/Barber%27s_pole
好像我小时候也问过这个问题
Barber's poleThe origin of the red and white barber pole is associated with the service of bloodletting and was historically a representation of bloody bandages wrapped around a pole.[2] During medieval times, barbers performed surgery on customers, as well as tooth extractions. The original pole had a brass wash basin at the top (representing the vessel in which leeches were kept) and bottom (representing the basin that received the blood). The pole itself represents the staff that the patient gripped during the procedure to encourage blood flow.
from http://en.wikipedia.org/wiki/Barber%27s_pole