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

Kaszuba...from Kaszuba? peasant stock?
Kasubinski...named changed in US during the 1940's.

Ryba (I know, fish)...Galilcian?

Maslanka (does it really mean buttermilk??)...is it a common name? My Maslanka relatives came from Swiatkowice near Warsaw...does this village/town still exist?

Koslowski...from the same area.

Thank you.