Swingle: an occupational name for a worker in the linen or hemp industry, from Middle English swingle, a wooden implement used for beating flax or hemp (Middle Dutch swinghel, from the verb 'to swing').
Swingle could possibly be an Anglicized spelling of the German or Swiss Zwingel, a topographic name from Middle High German zwingel meaning 'citadel.'
The name Swingle for branches in the United States is the Anglicized spelling of the German Schwingel.
Source: ancestry.com