Classical Mythology. any of a group of nymphs who were the companions of Artemis.
Origin: < L Orēad- (s. of Orēas) < Gk Oreiad- (s. of Oreiás), n. use of oreiás of the mountains, equiv. to órei(os) of the mountains (deriv. of óros mountain) + -as fem. patronymic suffix
c.1586, from L. Oreas (gen. Oreadis), from Gk. oreias "mountain nymph," from oros "mountain," probably from PIE base *er-/*or- "to raise" (cf. Skt. rsvah "high," L. oriri "to raise;" see orchestra).