IPA: /ˈpæsbʊk/
KK: /ˈpæsˌbʊk/
A small book used to record financial transactions, such as deposits and withdrawals, typically issued by a bank.
I checked my balance in my passbook after making a deposit at the bank.
Passbook → It is formed from "pass" (from Old French *passer*, meaning to go or move) and "book" (from Old English *bōc*, meaning a written work or record). A passbook is a book that allows the holder to record transactions, essentially a record of movement in and out of an account.
Think of a 'book' that helps you 'go through' your financial transactions — that's why a passbook is a record of your account activity.