The Mystkowski family is one of several noble families using the during the time of the PolishâÂÂLithuanian Commonwealth. First mention of the Mystkowski family comes from the Kodeks Dyplomatyczny Ksiestwa MAzowieckiego or 'The Diplomatic Code of the Duchy of Mazovia'. In this book, mention is made of a Comes Thomas (the Latin word Comes can be roughly translated as Count), the castellan of Nosylk, being granted the town of Myzlicow. Nosylk is the modern-day city of Nasielsk. Myzlicow is the modern town of Mystkowo, which is considered to be the ancestral land of the Mystkowski family.