burnt vs unproductive

burnt

adj
  • Being darker than standard, especially browner. 

  • Having a sunburn. 

  • Carbonised. 

  • Damaged or injured by fire or heat. 

unproductive

adj
  • No longer used to produce new words (see examples). 

  • Not productive; useless; fruitless. 

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