allowable vs permitable

allowable

adj
  • Permissible; tolerable; legitimate. 

  • Appropriate; satisfactory; acceptable. 

  • Intellectually admissible; valid; probable. 

  • Able to be added or deducted in consideration of something. 

noun
  • permitted amount or activity. 

permitable

adj
  • permissible 

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