freeze up vs shake in boots

freeze up

verb
  • To become cold and formal in demeanour. 

  • (of machines and software) To come to a sudden halt, stop working (functioning). 

  • To be adversely affected by ice, and not function. 

  • (of people and other animals) To stop or be stopped due to attentiveness, fear, surprise, etc. 

shake in boots

How often have the words freeze up and shake in boots occurred in a corpus of books? (source: Google Ngram Viewer )