regression vs underside

regression

noun
  • An analytic method to measure the association of one or more independent variables with a dependent variable. 

  • The reappearance of a bug in a piece of software that had previously been fixed. 

  • An equation using specified and associated data for two or more variables such that one variable can be estimated from the remaining variable(s). 

  • The making an exercise less straining to perform by manipulating the details of its performance like loaded weight, range of motion, angle, speed. 

  • The diminishing of a cellular mass like a tumor, or of an organ size. 

  • A psychotherapeutic method whereby healing is facilitated by inducing the patient to act out behaviour typical of an earlier developmental stage. 

  • An action of travelling mentally back in time. 

  • An action of regressing, a return to a previous state. 

underside

noun
  • The side that is below or underneath, the bottom. 

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