That nest egg in the bank that gets bigger each year with interest? That's an accrual — a sum of money, or benefit of some kind, that gets bigger over time.
Strictly speaking, an accrual doesn't have to be financial. Most religions believe you can obtain a spiritual accrual by doing good deeds on earth, for example. The origin of the word, as well as other similar terms such as accrue (the act of obtaining an accrual) come from the Latin word accrescere — meaning "to become larger."