piscina vs wellspring

piscina

noun
  • A basin or tank, especially one for holding fishes or for growing aquatic plants. 

  • A drained basin near a church's altar for the disposal of water from liturgical ablutions. 

wellspring

noun
  • The source of water for a stream, spring or well; a fountainhead; a wellhead. 

  • A perennial source of anything; a fountainhead of supply or emanation; resource. 

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