Etymology of Matrimony
Most dictionaries define matrimony quite simply: it is the position of being married, although it can also refer to the ceremony of marriage (e.g. holy matrimony).
The most interesting thing about this word is that it is a combination of the words mater (meaning mother) and monium (meaning state or condition or action).
In Latin, matrimony was spelled matrimonium.
It then evolved into the Old French matremoine before becoming matrimony in the late Middle English period.
Because this word has such deep roots in Latin, here’s a short summary of the related words:
Mater and matris are words that can be defined as mother, lady, matron or even source (in Latin texts you will often see them calling Rome the mater, meaning mother city).
Monia and monium are related to the words flumen (river, stream, flood; basically any liquid that flows) and nomen (sake, title, name, account).
The words mentum and menti are extensions of monia (chin; also a term for projecting edges in architecture).
Barnhart, Robert K., ed., Barnhart Dictionary of Etymology, H.W. Wilson Co., 1988.
Klein, Dr. Ernest, A Comprehensive Etymological Dictionary of the English Language, Amsterdam: Elsevier Scientific Publishing Co., 1971.
Lewis, Charlton T., Elementary Latin Dictionary, Oxford, 1890.
Liddell, Henry George, and Robert Scott, eds., Intermediate Greek-English Lexicon, Oxford Univ. Press, 1883.