Regino’s passage on the Pecheneg–Hungarian conflict is of crucial importance for the early history of the Hungarians. Regino was the first among the Latin authors who recorded the ethnonym Pecinaci. The aim of this paper is to analyse the ethnonym Pecinaci and determine how the information on the Pechenegs could reach Regino. There is a hypothesis among the historians that the information of the Pechenegs came to Regino through Byzantine mediation. But the Byzantine source of Regino is unknown. I suggest that the ethnonym Pecinaci reflects on a Slavic variant with the result of the second palatalization and it is probably not from Byzantine source. The final source of information came from the Hungarians. The information and the form of the ethnonym reached Regino via Northern Italy between 900 and 905 (or via the Hungarian–Moravian–Frankish borderland zone). The authenticity of Regino’s passage on the Pechenegs and the Pecheneg–Hungarian war were corroborated by Byzantine and Muslim sources.