Nowadays we think of a turnpike as one of those new super highways that roll across the country. Usually, it means one of these wonderful roads that collects a for the trip when the ride is done. Gates are set up from side to side and in order to pass through we must pay so much for each mile we have traveled on the new road. The money goes to maintain the road and perhaps to pay back some of the money which was borrowed to build it.
But the word turnpike is far older than super highways, far older even than automobiles. It goes way back to old farming days when public footpaths ran through the farmers fields. It was all right for people to use these paths, if they did not leave the gates open for the cattle to escape, To avoid this, turnstiles or turnpikes were set up between the fields. A person could get through by turning a spiked wheel through the gate, but the cattle could not, They were sometimes called turnpikes because the crossbars looked like spikey old weapons called pikes.
See why the modern turnpike borrowed its name from the old time turnpikes? The road or path is blocked until you overcome the snag. You must work the turnstile or pay the toll.