preloved vs unimproved

preloved

adj
  • Used; previously owned by somebody else. 

unimproved

adj
  • Not used or employed advantageously 

  • Not selectively bred for better quality or productiveness 

  • not tilled, built on, or otherwise improved for use. 

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