In Norse mythology, the goddess Rán and the jötunn Ægir both personify the sea, and together they have nine daughters who personify waves. Each daughter's name reflects poetic terms for waves. The sisters are attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources; the Prose Edda, composed in the 13th century; and in the poetry of skalds. Scholars have theorized that these daughters may be the same figures as the nine mothers of the god Heimdallr.
The Daughters of Ægir and Rán as depicted in a grayscale version of a painting by Hans Dahl (1849-1937)
Heimdallr Lifted by the Nine Wave Maidens by Karl Ehrenberg depicts Heimdallr's mothers as 'wave maidens' (German Wellenjungfrauen), 1882
The neck appears with Ægir's wave daughters in a piece by Swedish painter Nils Blommér, 1850, based on a poem by Arvid August Afzelius.
Nixie (folklore)
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The Nixie, Nixy, Nix, Näcken, Nicor, Nøkk, or Nøkken are humanoid, and often shapeshifting water spirits in Germanic mythology and folklore.
Nøkken by Theodor Kittelsen, 1904
Näckens polska by Bror Hjorth
Näcken ("The Water Sprite") by Ernst Josephson, 1884
The Neck as a brook horse by Theodor Kittelsen, a depiction of the Neck as a white horse