The Szczurowski clan of Szczurowo in the parish of Pniewnik in the Livland belongs to the Prus heraldic clan which is reliably confirmed by documents from the 15th and 16th centuries. The forefather of the Szczurowskis – Andrzej of Szczurowo – came from the Zakroczym County in the Zakroczym Land to the Liv Land in AD 1431. The name of Szczurowo was brought with him from the Zakroczym Land. The place of origin of his ancestors is uncertain, but there is some basis to believe that they came to the Zakroczym Land from the Grójec County in the Czersk Land. Probably in this area the forefathers of the Prus heraldic clan received first feoffments in the second half of the 13th century. They were Old Prussian refugees and they were named in the chivalric privilege of the dukes of Mazovia in AD 1345. It is impossible to determine the exact moment when the Prus heraldic clan forefathers came to Mazovia. Nonetheless, it is rationally justified to believe that it took place in the late sixties or the early seventies of the 13th century and was related to the Great Prussian Uprising against the Teutonic Order here is no certainty about which Old Prussian land is the place of origin of the Prus clan forefathers but we can be sure that they came to Mazovia and then scattered across the Polish-Lithuanian Commonwealth. The source documents analysis and application of the name criterion (paternal names inheritance) lead to the conclusion that the heirs of Szczurowo and probably related to them the heirs of Gościeńczyce are directly descended from Old Prussian knights named in the chivalric privilege of AD 1345. It is possible that they were related to 13th century Old Prussians from Pomesania and perhaps came from Sambia. Therefore, we can propose a cautious hypothesis that Sambia was the place of origin of the Prus heraldic clan forefathers