perihelion

Etymology

Formed from the obsolete word perihelium (“perihelion”) plus the suffix -ion, used for other names of apsides. Perihelium was borrowed from Late Latin perihelium, itself from Ancient Greek περι- (peri-, “around; surrounding”), which goes back to Proto-Indo-European *per- (“before, in front; first”), combined with ἥλιος (hḗlios, “sun”), which goes back to Proto-Indo-European *sóh₂wl̥ (“sun”). The word was modelled on perigeum (“point in an orbit about the Earth that is closest to the Earth, perigee”).