An Etymological Dictionary of Astronomy and Astrophysics

A faint false image caused by reflection that is sometimes seen in an optical system. In spectroscopy, a false image of a spectral line formed by irregularities in the ruling of diffraction gratings.

Etymology (EN): Ghost, from O.E. gast “soul, spirit, breath,” from P.Gmc. *ghoizdoz (cf. M.Du. gheest, Ger. Geist “spirit, ghost”), from PIE base *ghois- “to be excited, frightened;” cf. Av. zaēša- “horrible, frightful,” zôiždi&#353ta- “the most loathsome;” Mid./Mod.Pers. zešt “ugly, disgusting;” Goth. usgaisjan “to be afraid;” O.E. gæstan “to frighten.”

Etymology (PE): Parhib “ghost,” Pers. word of Xorâsâni dialect.