An Etymological Dictionary of Astronomy and Astrophysics

The great circle on the surface of a body formed by the intersection of the surface with the plane passing through the center of the body perpendicular to the axis of rotation. → celestial equator.

Etymology (EN): From M.L. æquator “equalizer” (of day and night, as when the sun crosses the equator), from æquare “to make equal, equate” + -tor.

Etymology (PE): Hamugâr, from hamug, → equal + -âr suffix forming agent nous (as in parastâr) or contracted present stem of âvardan “to bring; to cause, to produce.”