employ vs usage

employ

noun
  • The state of being an employee; employment. 

verb
  • To hire (somebody for work or a job). 

  • To use (somebody for a job, or something for a task). 

  • To make busy. 

usage

noun
  • The act of using something; use, employment. 

  • Custom, tradition. 

  • The established custom of using language; the ways and contexts in which spoken and written words are used, especially by a certain group of people or in a certain region. 

  • A custom or established practice. 

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