The surname Pirini is of anthroponymic origin and derives from dialectal forms related to the name Piero (a variant of Pietro). On this point F. De Laurentiis and E. Rossoni agree, linking it with variants such as Pirani and with hypocoristic forms proper to the local tradition.

E. Rossoni notes that it is an affectionate or diminutive form of the name Piero, documented already in the modern period, which confirms its use as a personal name before becoming fixed as a surname. In this way, the surname reflects the evolution of a given name in dialectal contexts, later consolidated as a hereditary surname.