Genealogy / THE MEANING AND RESEARCH OF MY POLISH LAST NAME, SURNAME? [4500]

hello and have a good day to all.
first of all, i am not of polish background,actually british/american.
i am however helping a friend with his polish heritage: the name has been changed many times.
ships manifest/passenger lists: Mronszynski/Mrowszynski Josef/Andreas/Jan

changes: Mrofchinski/Morfenski {todays spelling}
location Poland: Buchfelde, Znen-Znin-Cnen, town of Rosenau/Rosenan
Kreise, Posen,Poznan Preussen rule before 1900

hope above info will help in meaning of the surname, Mronszynski,Mrowszynski [misspelled?]
thank you.