Derived from Maryja (Polish for Mary):
* Marysia: This is a common and endearing diminutive form of "Maryja".
* Maryśka: A slightly more informal and playful version of "Marysia".
* Mery: This is a shorter, more modern nickname.
Other options:
* Małgosia: This is a nickname for "Małgorzata" (Margaret), which is a popular name in Poland. Since Margaret and Mary are related names, it might be used as a nickname for Mary as well.
Ultimately, the nickname used for Mary in Polish would depend on personal preference and the relationship between the people involved.