hieroglyphic vs understandable

hieroglyphic

noun
  • Undecipherable handwriting or secret symbol. 

  • Any symbol used in this system; a hieroglyph. 

  • A writing system of ancient Egypt, Minoans, Maya and other civilizations, using pictorial symbols to represent individual sounds as a rebus 

adj
  • difficult to decipher 

  • of, relating to, or written with this system of symbols 

understandable

adj
  • Capable of being accepted or excused under the circumstances. 

  • Capable of being understood; comprehensible. 

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