From Wikipedia

Gestapo - Hitler's Secret Police

Gestapo
(contraction of Geheime Staatspolizei: "Secret State Police") was the official secret police of Nazi Germany. Under the overall administration of the Schutzstaffel (SS), it was administered by the Reichssicherheitshauptamt (RSHA) ("Reich Main Security Office") and was considered a sister organization of the Sicherheitsdienst (SD) ("Security Service") and also a suboffice of the Sicherheitspolizei (SIPO) ("security police").

As part of the deal in which Adolf Hitler became Chancellor of Germany, Hermann Göring was named as Interior Minister of Prussia. This gave him command of the largest police force in Germany. Soon afterward, Göring detached the political and intelligence departments from the police and filled their ranks with Nazis. On April 26, 1933; Göring merged the two units as the Gestapo. He originally wanted to name it the Secret Police Office (German: Geheimes Polizeiamt), but discovered the German initials "GPA" would be too similar to the Soviet GPU