brass tacks vs pith

brass tacks

pith

noun
  • The essential or vital part; force; energy; importance. 

  • The spinal cord; the marrow. 

  • The soft, spongy substance in the center of the stems of many plants and trees. 

  • The albedo of a citrus fruit. 

  • The spongy interior substance of a feather or horn. 

  • One divided by pi. 

  • Power, strength, might. 

verb
  • To extract the pith from (a plant stem or tree). 

  • To kill (especially cattle or laboratory animals) by cutting or piercing the spinal cord. 

adj
  • The ordinal form of the number pi. 

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