divertimento vs serenade

divertimento

noun
  • composition that has several short movements, a style that composers started to use in the 18th century. 

serenade

noun
  • An instrumental composition in several movements. 

  • A love song that is sung directly to one's love interest, especially one performed below the window of a loved one in the evening. 

verb
  • To sing or play a serenade for (someone). 

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