ball lightning vs shooting star

ball lightning

noun
  • A short-lived glowing ball sometimes observed to float in the air and thought to consist of ionized gas associated with thunderstorms. 

shooting star

noun
  • A meteor, especially a streak of light in the night sky, caused by a meteoroid burning up as it enters the Earth’s atmosphere. 

  • Any of several wild flowering plants in the genus Dodecatheon, mostly found in Western North America. 

How often have the words ball lightning and shooting star occurred in a corpus of books? (source: Google Ngram Viewer )