deed vs letter of introduction

deed

noun
  • An action or act; something that is done. 

  • A legal instrument that is executed under seal or before witnesses. 

  • A brave or noteworthy action; a feat or exploit. 

  • Action or fact, as opposed to rhetoric or deliberation. 

verb
  • To transfer real property by deed. 

letter of introduction

How often have the words deed and letter of introduction occurred in a corpus of books? (source: Google Ngram Viewer )