plateau vs sap

plateau

verb
  • (of a varying quantity) To reach a stable level after a period of increase; to level off. 

noun
  • A comparatively stable level after a period of increase. 

  • A notable level of attainment or achievement. 

  • A largely level expanse of land at a high elevation; tableland. 

sap

verb
  • To exhaust the vitality of. 

  • To subvert by digging or wearing away; to mine; to undermine; to destroy the foundation of. 

  • To proceed by mining, or by secretly undermining; to execute saps. 

  • To make unstable or infirm; to unsettle; to weaken. 

  • To gradually weaken. 

  • To strike with a sap (with a blackjack). 

  • To pierce with saps. 

  • To drain, suck or absorb from (tree, etc.). 

noun
  • A narrow ditch or trench made from the foremost parallel toward the glacis or covert way of a besieged place by digging under cover of gabions, etc. 

  • The sapwood, or alburnum, of a tree. 

  • The juice of plants of any kind, especially the ascending and descending juices or circulating fluid essential to nutrition. 

  • Vitality. 

  • A naive person; a simpleton 

  • Any juice. 

  • A short wooden club; a leather-covered hand weapon; a blackjack. 

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