firman vs ultimatum

firman

noun
  • A royal decree issued by a sovereign in certain historical Islamic states, especially by the Sultan of Turkey. 

ultimatum

noun
  • A final statement of terms or conditions made by one party to another, especially one that expresses a threat of reprisal or war. 

How often have the words firman and ultimatum occurred in a corpus of books? (source: Google Ngram Viewer )