The authors agree that the surname derives from the personal name Leandro, of Greek origin. E. Rossoni notes that there are two possible etymologies: on the one hand, from the Greek Leiandros, compounded from leios ("calm") and andros ("man"), with the meaning "calm man"; on the other, from the Greek Leandros, formed from laos ("people") and andros ("man"), with the sense of "man of the people". F. De Laurentiis leans exclusively towards this second reading, holding that Leandro is a classical name going back directly to the Greek Léandros with that same meaning.

Rossoni describes the geographical distribution of the variants of the surname. Leandri has areas of presence in the region of Veneto, in the Perugia area —with localities such as San Giustino, Deruta, Città di Castello and Gualdo Cattaneo— and in Rome. The form Leandro, much rarer, appears in a small pocket between the provinces of Padua and Venice, and in Apulia, between the Bari and Taranto areas. The variant Leander, almost unique, is regarded as a dialect form of Leandri and is typical of Milan.