Deimos

satellite of Mars, discovered in 1877, named for Greek deimos, literally "fear, terror," also, as Deimos, the personification of such, regarded as a son of Ares, twin brother of Phobos"fear, panic, flight" (for which see phobia). Greek deimos is from PIE *duei- "fear," source also of Sanskrit dvesti "hate," Avestan duuaetha "threat," and possibly Latin dirus "fearful."