let-down vs miserable

let-down

noun
  • A disappointment or anticlimax. 

  • The clearance of an aircraft to descend through clouds to clear air below, or the process of granting such a clearance. 

  • The neurohormonal release of milk in dairy cows or in breastfeeding human mothers. 

miserable

noun
  • A state of misery or melancholy. 

  • A miserable person; a wretch. 

adj
  • In a state of misery: very sad, ill, or poor. 

  • Wretched; worthless; mean; contemptible. 

  • Very bad (at something); unskilled, incompetent; hopeless. 

  • Of the weather, extremely unpleasant due to being cold, wet, overcast, etc. 

How often have the words let-down and miserable occurred in a corpus of books? (source: Google Ngram Viewer )