 The hinge allowed it to 'open' or 'turn' This bar looked like the 'pike' used as a weapon in the army at that time and therefore we get 'turnpike'.The term was also used by the military for barriers set up on roads specifically to prevent the passage of horses.In addition to providing better surfaces and more direct routes, the turnpikes settled the confusion of the different lengths given to miles, which varied from 4,854 to nearly 7,000 feet.