An Etymological Dictionary of Astronomy and Astrophysics

That part of the electromagnetic spectrum, with a wavelength between 610 and 780 nm, that produces the impression of a variety of colors resembling that of blood.

Etymology (EN): M.E. red, from O.E. read (cf. Dan. rød, M.Du. root, Ger. rot), from PIE base *reudh- (cf. Av. raoidita- “red, reddish;” Skt. rudhirá- “red, bloody;” L. ruber “red;”
Gk. erythros “red”).

Etymology (PE): Sorx “red” (variants Tâleši sər, Kurd. sûr),
from Mid.Pers. suxr “red;” O.Pers. θuxra-; Av. suxra- “red, of fire-color;” Ossetic syrx, surx “red;” cf. Skt. śukrá- “clear, pure, bright.”