discoid vs placard

discoid

noun
  • A disk-shaped dental excavator designed to remove the carious dentin of a decayed tooth 

adj
  • Shaped like a disc/disk. 

placard

noun
  • The woodwork and frame of the door of a closet etc. 

  • A kind of stomacher, often adorned with jewels, worn in the fifteenth century and later. 

  • An extra plate on the lower part of the breastplate or backplate of armour. 

  • A sheet of paper or cardboard with a written or printed announcement on one side for display in a public place. 

verb
  • To announce with placards. 

  • To affix a placard to. 

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