off balance vs weak-kneed

off balance

prep
  • surprised; perplexed 

  • Not physical balanced; not having physical equilibrium. 

weak-kneed

adj
  • Used other than figuratively or idiomatically: see weak, kneed. 

  • Lacking will power or strength of character; timid. 

How often have the words off balance and weak-kneed occurred in a corpus of books? (source: Google Ngram Viewer )