lasting vs unsturdy

lasting

noun
  • A durable woollen material formerly used for women's shoes. 

  • The act or process of shaping footwear on a last. 

adj
  • Persisting for an extended period of time. 

unsturdy

adj
  • Not sturdy. 

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