back out vs invaginate

back out

verb
  • To reverse (a vehicle) from a confined space. 

  • To withdraw from something one has agreed to do. 

  • To exit a mode or function. 

  • To draw from behind the back [+accusative = a knife etc.] (as also bare back). 

  • To undo (a change). 

  • Coordinate terms: cancel, call off, get cold feet 

  • See also: sell short 

  • To dare (someone) to not withdraw from a challenge. 

  • To bet on someone losing. 

  • Coordinate term: scare off 

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 

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