invaginate vs regress

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 

regress

verb
  • To move backwards to an earlier stage; to devolve. 

  • To move from east to west. 

  • To perform a regression on an explanatory variable. 

  • To interrogate a person in a state of trance about forgotten elements of their past. 

noun
  • The act of passing back; passage back; return; retrogression. 

  • In property law, the right of a person (such as a lessee) to return to a property. 

  • The power or liberty of passing back. 

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