shifting vs travelling

shifting

noun
  • A shift or change; a shifting movement. 

  • The phenomenon by which two or more constituents appearing on the same side of their common head exchange positions to obtain non-canonical order. 

travelling

noun
  • The act of one who travels; a journey. 

adj
  • That travels (with one) 

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