knoll vs tump

knoll

noun
  • A small mound or rounded hill. 

  • A rounded, underwater hill with a prominence of less than 1,000 metres, which does not breach the water's surface. 

  • A knell. 

verb
  • To ring (a bell) mournfully; to knell. 

  • To sound (something) like a bell; to knell. 

  • To call (someone, to church) by sounding or making a knell (as a bell, a trumpet, etc). 

  • To arrange related objects in parallel or at 90 degree angles. 

tump

noun
  • A mound or hillock. 

  • A tumpline. 

verb
  • To form a mass of earth or a hillock around. 

  • To fall over. 

  • To draw or drag, as a deer or other animal after it has been killed. 

  • to bump, knock (usually used with "over", possibly a combination of "tip" and "dump") 

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