Etymology of Mercy
The concept of mercy is described by most dictionaries as a combination of compassion, kindness and/or forgiveness that is projected towards someone. This can be an enemy or a friend. In French, merci means thank you.
A number of Latin words indicate mercy: misereor, deprecor, clementia, misericordia, misereo, benignitas, exoratio, objaceo and eleyson to name a few.
Strangely enough, mercy doesn’t actually come from these words, but rather comes from the word merces, which, in fact, doesn’t mean mercy at all.
Merces is a Latin word that comes from merx (merchandise) and means something along the lines of rent, reward, salary, pay or bribe. It has everything to do with money, and nothing to do with mercy. Hey, it makes sense for something like mercenary, which do take money for their services.
The dawn of Christianity was what changed the meaning of this word so dramatically. To the Old French it started to mean something else: reward, blessing, decoration. But still, not mercy.
It was only when Old English arrived that this word was distorted into our present definition of mercy.
Mercy and Merci
As you may know, the French use merci to say “thank you”. They also do this in Catalonia as a way to say thanks. In French, mercy is usually written as miséricorde.
Mercy in Other Languages
Barnhart, Robert K., ed., Barnhart Dictionary of Etymology, H.W. Wilson Co., 1988.
de Vaan, Michiel, Etymological Dictionary of Latin and the other Italic Languages, Alexander Lubotsky ed., Leiden: Brill, 2008.
Lewis, Charlton T., Elementary Latin Dictionary, Oxford, 1890.
Liberman, Anatoly, Analytic Dictionary of English Etymology, University of Minnesota Press, 2008.
The Oxford English Dictionary, 2nd ed., Clarendon Press, 1989.
Tucker, T.G., Etymological Dictionary of Latin, Ares Publishers, 1976.