There have been several suggestions on the origin of the word Kashub. One being that the word Kashub is made up of the root "SZUBA" from the Arabic word "jubbah" and
the prefix "KA". "SZUBA" is seen in Persian as jubba, Italian as giubba, French jupe, Russian jubka, old Polish jupka, jupica and szuba. In the Polish of the middle ages
"jupka" meant "coat". The prefix "KA", which doesn't exist in contemporary Polish, in the middle ages had a meaning of something big and clumsy, and was used
Thus the Kaszubs were named for the coats they wore: "Those people in 'THOSE' coats." As you can see from the attached picture, their coats were really something to look at, and "ka" must have its roots in green-with-envy language.
According to he chronicler Bogufal, the first known historian to discuss the Kaszubs, as early as the 13th century the Kaszubs were well known for their coats.
They wore long wide coats which fell into folds, and he says that the word "Kaszub(i)" derives from kasaj huby, "folded coat", (or kasac huby, "to fold one's dress" - depending on who is the translator).
Later, in the 14th century, Dlugosz (another famous chronicler) wrote that the Kaszubs could easily be distinguished from their German neighbours by the fullness of their long overcoats.