happening vs inertia

happening

adj
  • Trendy, up-to-the-minute. 

  • Busy, lively; vibrant, dynamic; fashionable. 

noun
  • Something that happens. 

  • A spontaneous or improvised event, especially one that involves audience participation. 

inertia

noun
  • Lack of activity; sluggishness; said especially of the uterus, when, in labour, its contractions have nearly or wholly ceased. 

  • In a person, unwillingness to take action. 

  • The property of a body that resists any change to its uniform motion; equivalent to its mass. 

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