The "slot machine" term derives from the slots on the machine for inserting and retrieving coins. "Fruit machine" comes from the traditional fruit

on the spinning reels such as lemons and cherries.

to find time to see someone or do something between various other arrangements that have already been made: Doctor Meredith is busy this morning, but she might be able to slot you in around one o'clock. SMART Vocabulary: related words and phrases.