Glóredhel means "Elf of the Golden Light" in Sindarin (from glor- = "holy golden light" and edhel = "Elf"). She was so named because of her radiant blonde hair and height, which was comparable to an Elf.
Sindarin
glóredhel
feminine name. *Golden Elf
Gloredhel
Glóredhel
Daughter of Hador (S/158). Her name is a combination of glaur “gold” and Edhel “Elf” (SA/edhel, laurë).
Conceptual Development: In Silmarillion drafts from the 1930s, her name was first given as Glorwendil and Glorwendel, of unclear meaning (LR/310, 314).