mild vs thermal

mild

adj
  • Moderately warm, especially less cold than expected. 

  • Not sharp or bitter; not strong in flavor. 

  • Of only moderate severity; not strict. 

  • Not serious or dangerous. 

  • Gentle and not easily angered. 

  • Not overly felt or seriously intended. 

  • Acting gently and without causing harm. 

noun
  • A relatively low-gravity beer, often with a dark colour; mild ale 

thermal

adj
  • Providing efficient insulation so as to keep the body warm. 

  • Pertaining to heat or temperature. 

  • Caused or brought about by heat. 

  • Having a rough finish by treatment with a blow-torch. 

verb
  • To create a rough finish on stone by treating it with a high-temperature blow-torch. 

  • To fly an unpowered aircraft in a (thermal) column of rising air. 

noun
  • A column of rising air in the lower atmosphere created by uneven heating of Earth's surface. 

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