How did the idiom "chop and change" come from?

Hello, I'm glad to answer your question, monkey.

This is a story about a man who keeps a group of monkeys. He gave them three in the morning and four in the evening. Later, the monkeys were very dissatisfied, so the man changed to four in the morning and three in the evening. Monkeys thought it was too much, so they evolved into idioms. The above is all my reply, I hope I can help you and wish you a happy life ~