A small amount of money.
A small sum paid for a small service.
Something that is earned by a child.
An earning of someone low-paid.
I used to odd jobs when I was in high school to earn pin money.
My friend will finish project for you, for pin money.
You can buy iPhone with pin money.
It’s always good to have pin money set aside when running a business.
There is no origin for this idiom
Common phrase that has a specific meaning.