"point farthest from the sun" (of a celestial body's orbit), 1670s, from Mod.L. aphelium
, the modern form an alteration by Johannes Kepler, based on Gk. apo heliou
"away from the sun," from apo
"away from" + heliou,
gen. of helios
"sun" (see sol
). The whole was formed on the model of Ptolemaic apogæum
) to reflect the new helio-centric model of the universe.