on thin ice vs up for grabs

on thin ice

prep

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

adv

  • dangerously, hazardously, delicately 

up for grabs

adj

  • Available for anyone to obtain, claim, decide, or win. 

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