OriginVarious cultures throughout the world have similar figures. They were known to sing sailors to their deaths, like the Siren, or squeeze the life out of drowning men, while trying to rescue them.
EtymologyThe word mermaid is from the Middle English mere, in the obsolete sense 'sea' + maid(en). The Sirens of Greek mythology are sometimes portrayed in later folklore; in fact in some languages the name sirena is used interchangeably for both creatures.
Mermaids and their kinOther related types of mythical or legendary creature are water fairies (e.g. various water nymphs) and selkies.
Legend and mythTales of mermaids are nearly universal. The first known mermaid stories appeared in Assyria, ca. 1000 BCE. Atargatis, mother of Assyrian queen Semiramis, was a goddess who loved a mortal shepherd and in the process killed him. Ashamed, she jumped into a lake to take the form of a fish, but the waters would not conceal her divine nature. Thereafter, she took the form of a mermaid — human above the waist, fish below — though the earliest representations of Atargatis showed her as being a fish with a human head and legs, similar to the Babylonian Ea. The Greeks recognized Atargatis under the name Derketo, where she was often conflated with Aphrodite.
Lucian of Samosata in Syria (2nd century CE) in De Dea Syria ("Concerning the Syrian Goddess") wrote of the Syrian temples he had visited:
- "Among them - Now that is the traditional story among them concerning the temple. But other men swear that Semiramis of Babylonia, whose deeds are many in Asia, also founded this site, and not for Hera Atargatis but for her own Mother, whose name was Derketo"
- "I saw the likeness of Derketo in Phoenicia, a strange marvel. It is woman for half its length, but the other half, from thighs to feet, stretched out in a fish's tail. But the image in the Holy City is entirely a woman, and the grounds for their account are not very clear. They consider fishes to be sacred, and they never eat them; and though they eat all other fowls, they do not eat the dove, for she is holy so they believe. And these things are done, they believe, because of Derketo and Semiramis, the first because Derketo has the shape of a fish, and the other because ultimately Semiramis turned into a dove. Well, I may grant that the temple was a work of Semiramis perhaps; but that it belongs to Derketo I do not believe in any way. For among the Egyptians, some people do not eat fish, and that is not done to honor Derketo." 
Among the Neo-Taíno nations of the Caribbean the mermaid is called Aycayía  she of the beautiful voice. . Her attributes relate to the goddess Jagua, and the hibiscus flower of the majagua tree Hibiscus tiliaceous . Examples from other cultures are the Mami Wata of West Africa, the Jengu of Cameroon, the Merrow of Ireland and Scotland, the Rusulki of Russia, and the Greek Oceanids, Nereids, and Naiads. One freshwater mermaid-like creature from European folklore is Melusine, who is sometimes depicted with two fish tails, and other times with the lower body of a serpent. It is said in Japan that eating the flesh of a mermaid can grant unaging immortality. In some European legends mermaids are said to grant wishes.
It has been widely suggested that manatees or dugongs could be behind the myth of the mermaid. These large aquatic mammals are notable for the way in which they carry their young, cradled in their arms much as a human would carry a baby. It is possible that sailors seeing these unfamiliar beasts for the first time, would assume that they had in fact stumbled across some sort of humanoid species, and consequently spread their accounts of the sightings through their homelands on their return from voyages. It has even been posited that the traditional image of a mermaid with long flowing hair could be attributed to manatees breaking the ocean surface underneath patches of seaweed, and giving the unfamiliar observer the impression of having long hair. Prior to 546 B.C., the Milesian philosopher Anaximander proposed that mankind had sprung from an aquatic species of animal. For, he thought, man with his extended infancy could not have survived, originally, in the manner he does presently. This idea, based on elemental forces of mutation as opposed to evolution, does not appear to have survived Anaximander's death.
- Mermaids are one of the most famous creatures of popular culture, and are depicted regularly in literature and film. This is likely due to the influence of Hans Christian Andersen's fairytale The Little Mermaid (1836), which has been translated into many languages and adapted into various media. Andersen's portrayal has arguably become the standard, and has influenced most modern Western depictions of mermaids since it was published.