hair-splitting vs split hairs

hair-splitting

noun
  • the act of finding exceedingly small differences which are probably neither important nor noticeable to most people. 

split hairs

noun
  • Tedious details; minutiae. 

verb
  • To consider or argue about fine details; to worry about minutiae. 

How often have the words hair-splitting and split hairs occurred in a corpus of books? (source: Google Ngram Viewer )