Meaning of Mercer. French name. In French, the name Mercer means-Merchant.. Other origins for the name Mercer include-French, English, English, English.The name Mercer is a unisex name and can be used for a boy or girl name (male or female). French Name Meaning-Merchant.Origin-French.ther origins for the name Mercer include-French, English, English, English.The name Mercer is a unisex name and can be used for a boy or girl name (male or female). French Name Meaning-Merchant. Origin-French.