Marmennill

In Scandinavian folklore, a marmennill (also marmandill, marbendill, or margmelli) is a merman that often features in stories after having been accidentally caught at sea by fishermen. The creature is typically known for its ability to see the future or to reveal otherwise hidden knowledge, often laughing when he sees others acting foolishly.

Name
Marmennill has been variously translated as "merman", "mereman", "sea-mannikin" and "sea-goblin". In the Hauksbók version of Landnámabók, it is spelt as margmelli, with other medieval variants including marmandill. The modern Icelandic form is marbendill.

The name is also found as a component of the names of the species Millepora polymorpha and Corallina officinalis, which are known as marmendils-smíði ("the mermannikins work") and marmendils-þari ("the merman’s weed") respectively. It has been further suggested that the name of Merlin may be derived from marmenill.

Middle Ages
A marmennill is attested in Landnámabók:

Another prophetic marmennill appears in the 14th-century Hálfs saga ok Hálfsrekka. According to the saga, a father and son catch the marmennill on a fishing trip and subsequently present the creature to King Hjörleifr. The marmennill remains silent at the king's court, except for one bout of laughter. Upon being returned to the sea, however, he issues several prophecies in poetic verse.

Modern folklore
Stories about marmennill can be found in many modern Icelandic folklore collections, including in Jón Árnason's Íslenzkar þjóðsögur og æfintýri. One of the more well-known stories about the creature is known as Þá hló marbendill (And the marbendill laughed). It tells the story of a farmer who catches a marbendill out at sea and takes it home with him. On the way home, the creature laughs three times at the farmer. According to one account, the first time when his wife greets him, the second time when he hits his dog, and the third time when he trips over and attacks a tuft of grass. In exchange for his freedom, the creature reveals that he laughed at the farmer because his wife is unfaithful, his dog truly loves him, and the tuft of grass conceals a treasure. The farmer finally releases the creature and all that the creature claimed proves true.

Interpretation and discussion
It has been noted that similar to the marmennill, some other beings in Scandinavian folklore could give indications on future events such as the sea monsters hafstramba and margýgr, which often are seen before storms and shipwrecks, and Óðinn, who in Böglunda sögur forbodes a large battle and death. Furthermore, in both Landnámabók and Hrafnkels saga Freysgoða there are account of a being appearing in the dream of a settler of Iceland, telling him to move to another part of the island. In each case, the settler heeds the advice and avoids a landslide which killed the livestock that stayed behind.

Modern influence
The phrase þá hló marbendill ("then the merman laughed") is used in Iceland to refer to a sudden and spiteful fit of laughter in reference to the motif in folktales.