The origin of “portmanteau” is French and from the middle of the 16th century but the face of the word has changed, in French “portemanteau”. Besides the term are several different words which can be used for the same meaning, e.g. large travelling bag, valise or luggage. The word “porte” derives from the French word “porter” which means “to carry” and “manteau” translates to “mantle”. Furthermore there are two different plural forms of the term which are portmanteaus and portmanteaux.
The following link leads you to the Oxford Dictionary: