imperatorial vs regal

imperatorial

adj
  • Commanding; authoritative. 

  • Relating to the title or office of imperator. 

regal

adj
  • Of or relating to royalty. 

  • Befitting a king, or emperor. 

  • Befitting a king, queen, emperor, or empress. 

noun
  • A small, portable organ whose sound is produced by beating reeds without amplifying resonators. Its tone is keen and rich in harmonics. The regal was common in the sixteenth and seventeenth centuries; today it has been revived for the performance of music from those times. 

  • An organ stop of the reed family, furnished with a normal beating reed, but whose resonator is a fraction of its natural length. In the sixteenth and seventeenth centuries these stops took a multitude of forms. Today only one survives that is of universal currency, the so-called Vox Humana. 

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