mullion vs slat

mullion

verb
  • To shape into divisions by means of mullions. 

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

slat

verb
  • To construct or provide with slats. 

  • To set on; to incite. 

  • To slap; to strike; to beat; to throw down violently. 

  • To split; to crack. 

noun
  • A ski. 

  • A thin, narrow strip or bar of wood (lath), metal, or plastic. 

  • A control surface that extends forwards and downwards from the leading edge of a wing, leaving a gap between it and the leading edge, in order to modify the airflow around the wing so as to allow flight at a higher angle of attack without stalling, lowering the aircraft's stall speed. 

  • A thin piece of stone; a slate. 

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