An Etymological Dictionary of Astronomy and Astrophysics

Half of a sphere bounded by a great circle, especially one of the halves into which the earth or the celestial sphere is divided.

Etymology (EN): From L. hemisphærium, from Gk. hemisphairion, from hemi- “half,” (from PIE base *semi-; cf. Skt. sami, L. semi-, O.H.G. sami- “half,” and O.E. sam-) + sphaira, → sphere.

Etymology (PE): From nim-, → half + sepehr, koré,
→ sphere.