on thin ice vs unimportant

on thin ice

adv

  • dangerously, hazardously, delicately 

prep

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

unimportant

adj

  • petty; not important or noteworthy 

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