Naiad n.

*snā-, Proto-Indo-European root meaning "to swim," with extended form *(s)nāu- "to swim, flow; to let flow," hence "to suckle."

It forms all or part of: naiad; natant; natation; natatorial; natatorium; nekton; nourish; nurse; nursery; nurture; nutrient; nutriment; nutrition; nutritious; nutritive; supernatant.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit snati "bathes," snauti "she drips, gives milk;" Avestan snayeite "washes, cleans;" Armenian nay "wet, liquid;" Greek notios "wet, damp," Greek nan "I flow," nekhein "to swim;" Latin nare "to swim," natator "swimmer;" Middle Irish snaim "I swim," snam "a swimming."

word-forming element of Greek origin appended to nouns and denoting collective numerals (triad, Olympiad) and fem. patronymics (Dryad, Naiad, also, in plural, Pleiades, Hyades), thence also plant family names; from Greek -as (genitive -ados), fem. suffix equivalent to -is.

From its use in Iliad (literally "of Ilion," that is, "Troy;" from Ilias poiesis or oidos "poem of Ilion," the accompanying noun being feminine, hence the termination) it has formed titles of poems in imitation of it (Columbiad, Dunciad).

sea-nymph, in Greek mythology, late 14c., Nereides (plural), via Latin from Greek Nēreis (genitive Nēreidos), daughter of the ancient sea-god Nēreus, son of Pontus and Gaia, husband of Doris, whose name is related to naros "flowing, liquid, I flow" (see Naiad). In zoology, "a sea-centipede" (1840).

The most famous among them were Amphitrite, Thetis, and Galatea. The Nereids were beautiful maidens helpful to voyagers, and constituted the main body of the female, as the Tritons did of the male, followers of Poseidon or Neptune. They were imagined as dancing, singing, playing musical instruments, wooed by the Tritons, and passing in long processions over the sea seated on hippocamps and other sea-monsters. Monuments of ancient art represent them lightly draped or nude, in poses characterized by undulating lines harmonizing with those the ocean, and often riding on sea-monsters of fantastic forms.  [Century Dictionary]