heading vs siding

heading

noun
  • A strip of material at the hoist end of a flag, used for attaching the flag to its halyard. 

  • The end of a stone or brick which is presented outward. 

  • The direction into which a seagoing or airborne vessel's bow is pointing (apparent heading) and/or the direction into which it is actually moving relative to the ground (true heading) 

  • The title or topic of a document, article, chapter, or of a section thereof. 

  • Material for the heads of casks, barrels, etc. 

  • A gallery, drift, or adit in a mine; also, the end of a drift or gallery; the vein above a drift. 

  • The extension of a line ruffling above the line of stitch. 

siding

noun
  • A building material which covers and protects the sides of a house or other building. 

  • A second, relatively short length of track just to the side of a railroad track, joined to the main track by switches at one or both ends, used either for loading or unloading freight, storing trains or other rail vehicles; or to allow two trains on a same track to meet (opposite directions) or pass (same direction) (the latter sense is probably an American definition). 

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