A lot of phenomena in radiative transfer are named after a person who studied them (Rayleigh scattering, Mie scattering, Bragg diffraction, Kikuchi lines, Tyndall effect,...). Others are designated by a description of sorts of what is going on (geometric scattering, photon diffusion,...) But some are just the German word for what is going on, like gegenschein and bremsstrahlung. Sometimes "back-scatter" or "breaking radiation" is used, but just as often, the German word is used. Why is it that the German words stuck? Why German rather than another language, say Italian or Dutch?
German was the language of chemistry, physics and mathematics until the 1940s. Just today, I had to request two German translated papers in chemistry from the library. Anyone interested in doing a PhD in sciences had to show a reading knowledge of German, French or Russian and this requirement was determined by the field of study in American, British or Canadian universities. The term bremsstrahlung was coined by Sommerfeld, a German physicist. Since a majority of the natural scientists knew some functional German it was not a big deal to use this terminology occasionally. Another reason for keeping German words was that an English equivalent did not exist. Another famous term is convolution, for ages it remained as Faltung (folding).
In the late 60s and 70s, universities began to relax these conditions and by late 90s foreign language requirements vanished from the scene in the sciences. However, it is always beneficial to learn one more classical European language besides English in the sciences-if you wish to read original articles. Perhaps, that is why I think Harvard still requires a functional knowledge of one these languages: Chinese, French, German or Russian for a doctorate in mathematics. Fortunately, machine translation has become so good in the last two three years that scientific texts in German and French can be easily rendered into English even with extensive symbolism.
German was the main language of Physics, Chemistry, and Medicine during the second half of the 19th century and early 1900s. Besides being the language of the German Reich, it was also spoken and written across the very large Danubian monarchy. At that time, in Prague, Bucarest or Budapest, and even in Lemberg (Lvov/Lwiw today) the language of educated people was mostly German...