knock for a loop vs slog

knock for a loop

verb
  • To astonish; to stagger or overwhelm; to confuse or disorient. 

slog

verb
  • To work slowly and deliberately at a tedious task. 

  • To strike something with a heavy blow, especially a ball with a bat. 

  • To walk slowly, encountering resistance. 

noun
  • A long, tedious walk, or session of work. 

  • An aggressive shot played with little skill. 

How often have the words knock for a loop and slog occurred in a corpus of books? (source: Google Ngram Viewer )