firmness vs portability

firmness

noun
  • physical durability; rigidness (of material) 

  • security; steadfastness; good grip 

  • strictness; mental strength 

portability

noun
  • The quality of being portable. 

  • The ability of a program (or software system) to execute properly on multiple hardware platforms. 

  • The ability of an employee to move between different social security schemes without losing their contributions. 

  • The ability of a telephone subscriber to keep his/her number when switching to a different network. 

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