daybook vs account book

daybook and account book both are nouns.

Word	Noun	Adjective	Verb	Adverb
daybook	Yes	No	No	No
account book	Yes	No	No	No

As nouns, account book is a hypernym of daybook; that is, account book is a word with a broader meaning than daybook:

Other hypernyms of daybook include book, book of account, ledger, leger.

daybook (noun)	account book (noun)
an accounting journal as a physical object	a record in which commercial accounts are recorded
a ledger in which transactions have been recorded as they occurred