- matter-of-fact also matter of fact, 1570s as a noun, originally a legal term (translating L. res facti), "that portion of an enquiry concerned with the truth or falsehood of alleged facts," opposed to matter of law. As an adjective from 1712. Meaning "prosaic, unimaginative" is from 1787. Related: Matter-of-factly; matter-of-factness. German Tatsache is said to be a loan-translation of the English word.
Etymology dictionary. 2014.