pin money

a small amount of money that you earn and spend on things for yourself She has a part-time job that gives her pin money for extra treats for herself and the kids.

Small amounts of money for incidental expenses, as in Grandma usually gives the children some pin money whenever she visits. This expression originally signified money given by a husband to his wife for small personal expenditures such as pins, which were very costly items in centuries past. A will recorded at York in 1542 listed a bequest: "I give my said daughter Margarett my lease of the parsonage . . . to buy her pins." [Early 1500s]