let down vs uncompact

let down

verb
  • To reduce one's level of effort. 

  • To disappoint; to betray or fail somebody 

  • To soften in tempering. 

  • Used other than figuratively or idiomatically: see let, down. 

  • To allow to descend. 

  • To lengthen by undoing and resewing a hem. 

uncompact

verb
  • To expand from a compacted state; to uncompress computer data etc. 

adj
  • Not compact; incompact. 

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