Sinking fund
Money set aside a little each month for a known, irregular expense — so the bill is already covered when it arrives.
A sinking fund is an old, plain-English name for a simple technique: take an expense that shows up once or twice a year, divide the annual cost by twelve, and set that amount aside each month. When the bill lands, the money is already there.
A worked example. A $720 annual car insurance premium is $60 a month. Holiday and gift spending of $600 is $50 a month. Typical annual car repairs of $540 works out to $45. Together, $155 a month converts $1,860 of annual surprises into a steady transfer, and December stops damaging January.
A single savings account, with a running note of what belongs to what, is usually enough — separate accounts per fund are optional. A sinking fund is distinct from an emergency cushion: the fund is for the merely inconvenient and expected, the cushion is for the genuinely unforeseen. Keeping them separate protects both from being spent on the wrong thing.
Plumb is financial education, not financial, investment, tax, or legal advice.