Could Cybert be a polonized version of the English surname Seabert? For example when an ancestor read it out, he probably read it out s-y-b-e-r-t and and so Polish people understood it as c-y-b-e-r-t. Cybert is the surname of my great grandmother from my Dad's Mum's side of the family. And if so does that mean that one of my ancestors has possibly been English?
Probably the name polonised itself. Centuires ago most people were illiterate and even parish priests nad village scribes who basically knew how to read and write were often semi.literate at best. Any name which sounds alien to a given language community usuallay succumsb to the pronucniaotn pattern of the local community. Long before anyone had seen the name in writing (because most could not read or write!), they naturally started pronunouncing it Cybert. (The "tsi" sound of the original German Ziebert does not occur in Polish). By the time many generations later when people began learning to read and could sign their name, they pronounced it Cybert and wrote it down accordingly.
So I strongly doubt that one day in 1532 or 1710 some Ziebert decided: "Hey chaps, I'm gonna start spelling it C-y-b-e-r-t from now on!"
SOT: Several hundred people in Poland sign themselves Sot. It may have come from the Old Polish verb sotać (to fray, unravel); in modern Polish strzępić. But one cannot rule out some exterior source likeLow German sot meaning a spring or well. In French the adj. sot means silly or foolish.
