clump vs grex

clump

noun
  • A small group of trees or plants. 

  • A thick group or bunch, especially of bushes or hair. 

  • A cluster or lump; an unshaped piece or mass. 

  • A dull thud. 

  • A thick addition to the sole of a shoe. 

  • The compressed clay of coal strata. 

verb
  • To gather in dense groups. 

  • To form clusters or lumps. 

  • To walk with heavy footfalls. 

  • To strike; to beat. 

grex

noun
  • A kind of group used in horticultural nomenclature, applied to the progeny of an artificial cross from specified parents, in particular for orchids. 

  • A multicellular aggregate of amoeba. 

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