The authors agree that this surname derives from the name Negro, which continues in part the Latin cognomen Niger, formed from the adjective niger: "black". To a greater extent, however, it comes from its medieval use as a nickname or demonym, from the word negro (with the Latinizing or regional variant nigro), which besides referring to the colour of the skin, the hair or the beard, had acquired the sense of "belonging to black populations" and, in some regions, had become a synonym for Moor and Saracen.

E. De Felice notes that the surname is distributed throughout Italy, with well-differentiated regional variants: Lo Nigro in southern Italy; Nigri and Nigris in Friuli-Venezia Giulia; Nigra in Piedmont; Nigriello in the Naples area; Negrisoli in Emilia-Romagna and Veneto; and apocopated forms also in Veneto.