overburden vs swarm

overburden

verb
  • To overload or overtax. 

noun
  • A sterile stratum that lies above the stratum being investigated 

  • The rock and subsoil that lies above a mineral deposit such as a coal seam. 

swarm

verb
  • To overwhelm as by an opposing army. 

  • To fill a place as a swarm. 

  • To climb by gripping with arms and legs alternately. 

  • To breed multitudes. 

  • To move as a swarm. 

  • To teem, or be overrun with insects, people, etc. 

noun
  • A mass of people, animals or things in motion or turmoil. 

  • A large number of insects, especially when in motion or (for bees) migrating to a new colony. 

  • A group of nodes sharing the same torrent in a BitTorrent network. 

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