Wikipedia
Szmalcownik , in English also spelt shmaltsovnik, is a pejorative Polish slang word used during World War II that denoted a person blackmailing Jews who were hiding, or blackmailing Poles who protected Jews during the Nazi occupation.
The term's origins is the word szmalec ( Polish: dough, literally "lard"), emphasizing money as the most important reason behind blackmailing.
The Polish Secret State considered szmalcownictwo an act of collaboration with the German occupiers. The Armia Krajowa (Home Army) punished it with the death sentence as a criminal act of treason. Blackmailers had been sentenced to death by the Special Courts of the Polish Underground for crimes against Polish citizens. The Polski Komitet Wyzwolenia Narodowego (Polish Committee of National Liberation) by its decree of 31 August 1944 also condemned this act as collaboration with Nazi Germany. This decree is still a valid law in Poland, and any person who committed an act of szmalcownictwo during the war faces life imprisonment.
Gunnar S. Paulsson estimates that the total number of szmalcowniki in Warsaw were "as high as 3-4 thousand". The damage that these criminals did was substantial. Most were interested in money. By stripping Jews of assets needed for food and bribes, harassing rescuers, raising the overall level of insecurity, and forcing hidden Jews to seek out safer accommodation, blackmailers added significantly to the danger Jews faced and increased their chances of getting caught and killed. At the beginning of the German occupation, szmalcowniks were satisfied with a few hundred zlotys in extortion, but after the death penalty for hiding Jews was introduced the sums rose to several hundred thousand zlotys.
Germans sometimes treated szmalcowniks as criminals and imposed punishments on them. The reason was that szmalcowniks also bribed German officials and policemen — after the denunciation of a rich Jew, szmalcowniks and corrupted Germans shared the robbed money.