Many early highways had entrances that were blocked by a pike, or long pole, which was “turned,” or opened, after a toll was paid.
These highways were called turnpikes.
Those who walked these roads were sometimes vagrants and very often unsophisticated farm boys on their way to seek their fortunes in the city.
If you just “came down the pike” you were naive and often admonished as a “piker.”
A small-time player is also known as a “piker”.