Merrow
Merrows are the merfolk of Tír na nÓg. They have fishtails when underwater, but legs on land. The Seelie merrows live in the Coral Court.
Merrows wear a special hat called a cohuleen druith, which enables them to dive beneath the waves. If they lose this cap, it is said that they will lose their power to return beneath the water.
Said to be of "modest, affectionate, gentle, and [benevolent] disposition", the merrow is believed "capable of attachment to human beings", with reports of inter-marriage. One such mixed marriage took place in Bantry, producing descendants marked by "scaly skin" and "membrane between fingers and toes". But after some "years in succession" they will almost inevitably return to the sea, their "natural instincts" irresistibly overcoming any love-bond they may have formed with their terrestrial family.[ And to prevent her acting on impulse, her cohuleen druith (or "little magic cap") must be kept "well concealed from his sea-wife".
Merrow-maidens have also been known to lure young men beneath the waves, where afterwards the men live in an enchanted state. While female merrows were considered to be very beautiful, the mermen were thought to be very ugly. This fact potentially accounted for the merrow's desire to seek out men on the land. Merrow music is known to be heard coming from the farthest depths of the ocean, yet the sound travels floatingly across the surface. Merrows dance to the music, whether ashore on the strand or upon the wave. - Wikepedia
In Mythology and Folklore:
The merrow-maiden is like the commonly stereotypical mermaid: half-human, a gorgeous woman from waist up, and fish-like waist down, her lower extremity "covered with greenish-tinted scales" (according to O'Hanlon). She has green hair which she fondly grooms with her comb. She exhibits slight webbing between her fingers, a white and delicate film resembling "the skin between egg and shell".Merrows wear a special hat called a cohuleen druith, which enables them to dive beneath the waves. If they lose this cap, it is said that they will lose their power to return beneath the water.
Said to be of "modest, affectionate, gentle, and [benevolent] disposition", the merrow is believed "capable of attachment to human beings", with reports of inter-marriage. One such mixed marriage took place in Bantry, producing descendants marked by "scaly skin" and "membrane between fingers and toes". But after some "years in succession" they will almost inevitably return to the sea, their "natural instincts" irresistibly overcoming any love-bond they may have formed with their terrestrial family.[ And to prevent her acting on impulse, her cohuleen druith (or "little magic cap") must be kept "well concealed from his sea-wife".
Merrow-maidens have also been known to lure young men beneath the waves, where afterwards the men live in an enchanted state. While female merrows were considered to be very beautiful, the mermen were thought to be very ugly. This fact potentially accounted for the merrow's desire to seek out men on the land. Merrow music is known to be heard coming from the farthest depths of the ocean, yet the sound travels floatingly across the surface. Merrows dance to the music, whether ashore on the strand or upon the wave. - Wikepedia
From The Books:
Two giant wooden merrows arched overhead, visible to the whole market. Their floating wooden hair met at the top, and their curved fish’s tails sprang out of the stone platform.Article by Hanna Sandvig