merces

Merces, mercedis, f., third declension. It is the pay for work or for a service - wages, rent, a fee - and never the goods themselves. Those are merx, mercis, a different noun from the same commercial root, and confusing the two turns a wage packet into a cargo.

The Vulgate gives it a second life. Merces there is the return God makes for what a person has done, so merces vestra copiosa est in caelis reads like a payslip in Latin and does not in English, and translators have to decide between "wage" and "reward" line by line. The man who works for one is a mercenarius. English mercenary comes straight from that, and merchant, market and commerce come from merx alongside it.