Also,  
  know a thing or two 
  ;  
  know it all 
  ;  
  know one's way around 
  . Be extremely knowledgeable or experienced. These idioms may be used somewhat differently, expressing overconfidence, as in  
  Helen always knew all the answers, or thought she did 
  , or competence, as in  
  Bob knows a thing or two about battery technology 
  , or ruefulness, as in  
  I thought I knew it all about plants and then I got poison ivy 
  , or genuine expertise, as in  
  John knows his way around tax forms 
  . The first term dates from the early 1900s, the second from the later 1700s, the third from the later 1800s, and the fourth, also put as  
  know one's way about 
  , dates from the 1500s. Also see       ; under