Old Testament vs Holy Writ

Old Testament and Holy Writ both are nouns.

Word	Noun	Adjective	Verb	Adverb
Old Testament	Yes	No	No	No
Holy Writ	Yes	No	No	No

Old Testament (noun)	Holy Writ (noun)
the collection of books comprising the sacred scripture of the Hebrews and recording their history as the chosen people; the first half of the Christian Bible	the sacred writings of the Christian religions