Just had to nitpick the thread title...
BTW, the proper spelling is 'Gestapo' and is actually an acronym for the German word
Geheime Staatspolizei (Secret State Police). Their unlimited police powers in silencing opponents of the Nazi regime in WW II gave rise to the modern word 'Gestapo tactics' in referring to heavy-handed enforcement of laws, rules and regulations. The Infernal Revenue Service (oops... Internal Revenue Service) has usually been likened to the 'Tax Gestapo', for its ruthless and sometimes unconstitutional enforcement of the tax laws.
Other WWII German abbreviations and words that entered modern English:
Flak - Abbreviation for
Fliegerabwehrkanone (anti-aircraft cannon). This word was brought home by the B-17 and B-24 aircrews that flew missions over Germany, and 'catching flak' is now a common term for getting chewed out.
Stuka - Abbreviation for
Sturzkampfflugzeug (dive bomber). The Junkers JU-87 airplane, while notorious in its role as a dive bomber in the early days of WW II, suffered heavy losses during the Battle of Britain. Later models of the Stuka served as effective tank busters.
Blitz - The word by itself means 'lightning' but was actually shortened from the word
Blitzkrieg (lightning war); from the tactics used by the Germans to achieve quick surprise on the battlefield in the early years of WWII. Today, you'll hear the word 'blitz' to refer to football plays.
Strafe - Actually means 'punishment', but used nowadays to refer to low level machine-gun or rocket attack by airplanes.