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nymph of the woods, 1550s (plural Driades is attested from late 14c.), from Latin dryas, from Greek dryas (plural dryades) "wood nymph," from drus (genitive dryos) "oak," from PIE root *deru- "be firm, solid, steadfast," with specialized senses "wood, tree." Related: Dryadic.

in Greek and Roman mythology, "water nymph," one of the female deities presiding over springs and streams, c. 1600, from Latin Nais, Naias (genitive naiadis), from Greek Naias (plural Naiades) "river nymph," from naiein "to flow," from PIE *naw-yo-, suffixed form of *(s)nau- "to swim, flow, let flow" (from PIE root *sna- "to swim"). Dryden used the Latin singular form Nais, and the plural Naiades is attested in English from late 14c.