An Etymological Dictionary of Astronomy and Astrophysics

The locus of a point the sum of whose distances from two fixed points is constant.

Etymology (EN): From O.Fr. ellipse, from L. ellipsis “ellipse,” also, “a falling short, deficit,” from Gk. elleipsis “an omission,” from el-, variant of en-, + leip-, stem of leipein “to leave” + suffix -sis.

Etymology (PE): Beyzi, from Ar.