pinprick vs spherule

pinprick

noun
  • A very tiny dot. 

  • A mildly annoying wound or damage. 

  • An insignificant puncture made by a pin or similar point. 

verb
  • To produce a jabbing sensation, like a pinprick, in. 

  • To puncture with a tiny hole or holes. 

spherule

noun
  • A small sphere. 

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