It was suggested but never validated that the swords used in the North East rapper dance were used down mines for cleaning the dirt off the backs of pit ponies. If that were true they could also be used to tap signals to the banksman in charge of the cage. Not just up and down but speed as well - Materials were winched faster than men. So, Rapper being both the signaller and device and the banksman being the recipient, rapper to t'bank makes sense!