napkin vs pocket square

napkin

noun
  • A small scarf worn on the head by Christian women (chiefly Roman Catholic and Eastern Orthodox) when entering a church, as a token of modesty. 

  • A serviette; a (usually rectangular) piece of cloth or paper used at the table for wiping the mouth and hands for cleanliness while eating. 

  • A nappy (UK), a diaper (American). 

pocket square

noun
  • A handkerchief worn in a breast pocket as an accessory to a suit. 

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