Grischa (alternatively spelled Grisha or Gricha) is a short form for the name Gregory or Grigorij, and sometimes for the name Georgi as well, used in Russia and some nearby countries, including Ukraine and Bulgaria. The "sha" ending is a typical short form in the Russian language for names. Other such short forms include Natasha for Natalia, Sasha for Alexander, Alyosha for Alexei, and Misha for Michael (or Mikhail, which is the Russian spelling).
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Grischa Wikipedia(Text) CC BY-SA