apsis vs perihelion

apsis

noun
  • Either of the points in the elliptical orbit of a planet or comet where it is closest or furthest from the sun; perihelion or aphelion; an apside 

  • A recess or projection, with a dome or vault, at the east end of a church; an apse. 

perihelion

noun
  • The point in the elliptical orbit of a comet, planet, etc., where it is nearest to the Sun. 

  • The highest point or state; the peak, zenith. 

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