interpreting vs set phrase

interpreting

noun
  • Synonym of interpretation (an act of interpreting or explaining what is obscure) 

  • Synonym of interpretation (the discipline or study of translating one spoken or signed language into another) 

set phrase

noun
  • An idiomatic expression in general. 

  • An established expression whose wording is subject to little or no variation, and which may or may not be idiomatic. 

How often have the words interpreting and set phrase occurred in a corpus of books? (source: Google Ngram Viewer )