The authors agree that the surname originates in the personal name of Germanic root Lanfrancus, compounded from landa ("territory, country") and franka ("free, brave"). E. De Felice notes that the name is documented in northern Italy from the 9th century and in Tuscany from the 11th, with a tradition that may be either Frankish or German, and proposes as its original meaning "free in his own country". R. Brondolo agrees on the Germanic base and on the antiquity of the name, to which he attributes the sense of "free and strong man in his own land".

E. Rossoni supplies concrete historical documentation: an architect named Lanfrancus active in Modena around the year 1000, who built the cathedral between 1099 and 1106; a Lanfrancus Ferrarius cited in 1130 among the captains of Milan; and notaries of that name in the Codex Diplomaticus Brescianus in 1147 and 1185. Around 1200, in San Casciano (Pisa), references appear to families identified as de domo Lanfranchi, and in Florence a Ugo filius Guidi Lanfranchi is recorded. As for distribution, Rossoni indicates that Lanfranchi is typical of Lombardy and upper Emilia-Romagna, with a presence also in the Florence area.

V. Blunda documents the surname in Sicily with the same Germanic base, and mentions as a notable historical figure Lanfranc of Pavia (c. 1005–1089), a Lombard Benedictine monk who was prior of the Norman abbey of Bec and later archbishop of Canterbury under William the Conqueror, with a central role in the reorganization of the English Church after the Norman conquest of 1066. The surname is further held to have an anthroponymic root related to the Germanic Landfrank, read as "free and brave patriot", with a documented presence in the Val Seriana.