invaginate vs topple

invaginate

verb
  • To turn or fold inwardly. 

  • To fold inward to create a hollow space where none had existed, as with a gastrula forming from a blastula. 

  • To fold up or enclose into a sheath-like or pouch-like structure, either naturally or as part of a surgical procedure. 

adj
  • Having one portion of a hollow organ drawn back within another portion. 

  • sheathed 

topple

verb
  • To totter and fall, or to lean as if about to do so. 

  • To overturn 

  • To overthrow something. 

  • To push or throw over 

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