pin money 
noun [mass noun]
A small sum of money for spending on inessentials: working two days a week in the boutique gave her a little pin money...
- When they moved out, shame-free Adrienne started making inquiries about government compensation for her lost pin money.
- Far from ‘having it all’ - the career, the husband, the kids - it seems that working motherhood, for many women, means a part-time job, pin money and some activity outside the home.
- My husband didn't like me to work full time, so I was cleaning banks and doctors' surgeries for pin money.
Origin
Late 17th century: from pin in the sense 'decorative clasp for the hair or a garment' + money. The term originally denoted an allowance made to a woman for dress and other personal expenses by her husband.