It is often used in modular networking devices. Slot: A slot is a space within a chassis or device where a module or card can be inserted. It provides the physical and electrical connections for the module or card to function within the larger networking device.
The "slot machine" term derives from the slots on the machine for inserting and retrieving coins. "Fruit machine" comes from the traditional fruit
fruit slots
on the spinning reels such as lemons and cherries.