on wheels vs separable

on wheels

prep
  • Used other than figuratively or idiomatically: see on, wheels. (Having wheels affixed to the bottom, and so transportable; synonym of wheeled). 

  • Mobile; able to be moved; especially, synonym of on the move. 

  • To a large degree, excessively. 

separable

adj
  • Able to be separated. 

  • Able to be brought to a form where all occurrences of the dependent and the independent variable are on opposite sides of the equal sign. 

  • Having a countable dense subset. 

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