legation vs power of attorney

legation

noun
  • The purpose for which a legate is sent; a legate's mission or commission. Now rare (cf. OED) 

  • The post or office of a legate; a legateship. 

  • A diplomatic mission. 

  • The official residence of a diplomat. 

power of attorney

noun
  • The legal authorisation of one person to act as the agent of another. 

  • A legal document allowing one person to act as the agent of another. 

How often have the words legation and power of attorney occurred in a corpus of books? (source: Google Ngram Viewer )