Counterman

noun

1. A man who tends a counter, as in a diner.
2. A salesman in a shop or store; the man behind the counter, as distinguished from the floor-walker, etc.
3. A man who attends at the counter of a shop to sell goods.
4. A man who serves behind a counter, especially in a diner.
5. someone who attends a counter (as in a diner)