harp vs psalterium

harp

noun
  • A musical instrument consisting of a body and a curved neck, strung with strings of varying length that are stroked or plucked with the fingers and are vertical to the soundboard when viewed from the end of the body 

  • Any instrument of the same musicological type. 

  • A grain sieve. 

  • A harmonica. 

verb
  • To repeatedly mention a subject. 

  • To play (a tune) on the harp. 

  • To play on (a harp or similar instrument). 

psalterium

noun
  • A psaltery (zither-like musical instrument) 

  • An omasum. 

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