The consulted works concur in deriving this surname from the Italian word pellegrino, meaning "pilgrim" or "traveler," itself from the Latin adjective peregrinus, which originally referred to a foreigner or someone traveling far from home. During the Middle Ages, the byname was given to those who undertook pilgrimages to sacred sites such as Rome, Jerusalem, or Santiago de Compostela, and in time it became a surname. The source Surnames in Italy also notes that in some cases the term could simply denote a "foreigner" or "stranger," and that the surname may additionally derive from place names such as Pellegrina, San Pellegrino, or San Pellegrino Terme.

R. Brondolo proposes a more specific etymology, tracing the word back to the Latin phrase per agros, with the sense of "wanderers through the empty fields," in allusion to those who traveled to the Holy Land. He draws a parallel with surnames such as Palmieri — those who carried a palm branch — and Gallizia — pilgrims to the shrine of Santiago — presenting them as analogous cases of surnames rooted in medieval devotional practices.

E. Giraudo documents the form Petrus Pellerinus in 1228, which attests the use of the appellative from at least the thirteenth century. His analysis focuses on the area of Cuneo, with a notable presence in Boves, Borgo San Dalmazzo, and Tarantasca.

A. Bongioanni notes that pellegrino also functioned as a given name, associated with a fourth-century saint celebrated on August 1, and that the feminine form Pellegra is also recorded. He further observes that the variants Pelarini and Pellarini are characteristic of Friuli-Venezia Giulia, and draws a comparison with the French pèlerin.

E. Rossoni documents the surname across Veneto, Lombardy, Tuscany, and southern Italy, with variants formed through suffixes such as -ini, -etti, and -elli, which are frequent in patronymic and affectionate surname formations. Among the recorded variants are Pellegrin, Pellegrinelli, Pellegrinetti, Pellegrinotti, Pellegrineschi, Pellegrinon, Depellegrin, and Pellegrinet. The source Surnames in Italy adds that the suffixes -et and -on are typical of northeastern Italy, influenced by Friulian, Slovene, or German dialect traditions, and that the prefix De- in Depellegrin may indicate noble or local origin.