backtrack vs invert

backtrack

verb
  • To retrace one's steps. 

  • To exercise a racehorse around the racetrack in the opposite direction to that in which races are run. 

  • To taxi down an active runway in the opposite direction to that being used for takeoff. 

  • To repeat or review work already done. 

noun
  • the act of backtracking 

invert

verb
  • To turn (the foot) inwards. 

  • To divert; to convert to a wrong use. 

  • To turn (something) upside down or inside out; to place in a contrary order or direction. 

  • To move (the root note of a chord) up or down an octave, resulting in a change in pitch. 

  • To undergo inversion, as sugar. 

adj
  • Subjected to the process of inversion; inverted; converted. 

noun
  • The base of a tunnel on which the road or railway may be laid and used when construction is through unstable ground. It may be flat or form a continuous curve with the tunnel arch. 

  • A skateboarding trick where the skater grabs the board and plants a hand on the coping so as to balance upside-down on the lip of a ramp. 

  • An invertebrate. 

  • An inverted arch (as in a sewer). 

  • An elevation of a pipe at a certain point along the pipe. 

  • The lowest point inside a pipe at a certain point. 

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