Phosphorus

Phosphorus was the personification of the morning star. He was the son of Astraeüs (or Cephalus) and Eos, and his name can be interpreted either as 'light bringer' (phos, 'light' and phero, 'to bring') or 'dawn-bringer' (eos, 'dawn', as for Eos, and phero).

His Roman equivalent, whose name means exactly the same as the first of these, is Lucifer. The chemical substance took its name not from him but independently from the Greek adjective phosphoros, 'light-bearing'.