The story
Blend of X + Twitter following the rebranding of Twitter to X, motivated by the pronunciation of shitter, with the pronunciation of initial ⟨X⟩ as /ʃ/ potentially influenced by Portuguese or Pinyin, as in the name of Xi Jinping (pronounced /ʃiː/ in English). Compare Xitler (a homophone of Shitler).
Etymology from Wiktionary, CC BY-SA 4.0.