blue-skies vs unserviceable

blue-skies

adj

  • Unrealistic or impractical. 

  • Of no immediate practical application. 

unserviceable

adj

  • Impractical. 

  • Not working (machinery, etc). 

  • Unusable; of no use. 

How often have the words blue-skies and unserviceable occurred in a corpus of books? (source: Google Ngram Viewer )