https://en.wikipedia.org/wiki/Beefsteak_Nazi
Beefsteak Nazi was a term used in Nazi Germany to describe Communists who joined the Nazi Party. 'Beefsteak Nazis' appeared following the suppression of the German Communist Party in the 1930s, and the term was popular as early as 1933. The term was particularly used of working-class members of the Sturmabteilung (SA) who were aligned with Strasserism. The term derived from the idea that these individuals were like a 'beefsteak' - brown on the outside and red on the inside, with 'brown' referring to the colour of the uniforms, and 'red' to their communist sympathies.