on thin ice vs unsafe

on thin ice

adv
  • dangerously, hazardously, delicately 

prep
  • In a dangerous, hazardous, or delicate situation; at risk. 

unsafe

adj
  • Not safe (various senses); dangerous. 

verb
  • To remove the safety from (a weapon). 

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