untold vs zillion

untold

adj
  • Not told; not related; not revealed; secret. 

  • Not able to be counted, measured, told, expressed in words, or described; extremely large in scale, number, quantity, suffering, damage, etc.; uncountable, unmeasurable, immeasurable, indescribable, inexpressible. 

  • Not numbered or counted. 

zillion

noun
  • An unspecified large number (of); a gazillion. 

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