An Etymological Dictionary of Astronomy and Astrophysics

Any of the tubes forming part of the blood circulation system of the body, carrying mainly oxygen-depleted blood towards the heart (OxfordDictionaries.com).

Etymology (EN): M.E. veine, from O.Fr. veine “vein, artery, pulse,” from L. vena “a blood vessel,” also “a water course, a vein of metal,” of unknown origin.

Etymology (PE): Siyâhrag, literally “black vessel,” from siyâh, → black, + rag, → vessel.