Congratulations on obtaining your ancestor's birth certificate. Westpreußen is the German rendering of Westpreussen ('ß' rather than 'B' is the double 'ss' in German orthography, though some claim it stands for 'sz'). Your ancestor Klemens (Clemens is the old orthographic conventional spelling, whereas Klemens is the modern convention's "Rechtschreibung" spelling. The "Rechtschreibung" was [and remains] a spelling reform movement,whose name means correct spelling/writing or 'orthography') probably changed his name from Zirotzki to Zierold during World War II in order to emphasise his German-ness in a time and place when it was extremely disadvantageous to be considered Polish. The reality is that prior to WWII many mixed marriages occurred between ethnic Germans and ethnic Poles in West Prussia and many other areas of central and eastern Europe giving rise to people who were of mixed ethnic heritage. Some became entirely germanised, while others were polonised. In Austrian Bukovina, there were three lines of the Zurowski family. Through intermarriage, the senior line remained predominantly Polish-speaking and Roman Catholic, the second line (mine) due to my ancestor's marriage with two Bohemian German wives (in succession, of course!) became German-speaking though still Roman Catholic, and the youngest line became Romanianised and Orthodox, because the male founder of that line married the daughter of a local ethnic Romanian magistrate. Of course, in Bukovina as in West Prussia, though under two separate crowns (the Austrian vs the German) in the 19th century, many of the inhabitants were bilingual or even multilingual, and many straddled the line between two or more cultures. The divisive racial policies of Hitler's Germany caused many ethnicly-mixed people to opt to identify with the 'prestige' group, at that time, of course, the Germans. It was probably as a matter of survival as well as various psychological reasons that Klemens Zirotzki changed his name (probably with the full knowledge of the German authorities, who were noted for their thorough-going bureaucratic oversight) to Zierold in reflection of his desire to be treated as a member of the "Master Race" as opposed to one of the Poles who were often sent to Germany's industrial heartland as slave labourers, and who were subjected to many other forms of racial discrimination under the German occupation of the short-lived free Polish republic which had been German territory before World War I.