mullion vs rung

mullion

noun
  • A vertical bar between the panes of glass or casements of a window or the panels of a screen. 

verb
  • To shape into divisions by means of mullions. 

rung

noun
  • A crosspiece forming a step of a ladder; a round. 

  • A position in a hierarchy. 

  • A crosspiece between legs of a chair. 

verb
  • simple past tense of ring 

adj
  • Of a pig: having a ring through the nose. 

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