The scholars consulted agree that this surname derives from a nickname formed from marchese, a term that in the Middle Ages designated the feudal lord of a marca — that is, a frontier county — and that over time became a noble title ranking immediately below that of duke.

E. De Felice notes that the nickname was given mainly to those who maintained relations of dependence with a marquess, or else in figurative senses no longer recoverable. R. Brondolo adds that such dignitaries represented the authority of the march, acting in the marquess's stead. F. De Laurentiis confirms the general etymology without contributing information substantially different from De Felice's. It is also noted that the surname bears a formal resemblance to Marchiondi.

Regarding geographical distribution, De Felice observes that the form Marchese predominates in southern Italy and in Liguria, while Marchesi — the form treated here — is concentrated in northern Italy. He further records the variant Marchesich, proper to the area of Friuli-Venezia Giulia, and the forms Marchesini and Marchesìn, predominant respectively in Emilia-Romagna and in Veneto.