The name Iara originates from the word yiara of the extinct Tupi language of the native Brazilians, which stands for the lady of the lake. Often called the Mother of the Waters, Iara in Brazilian mythology is a mermaid-like creature and can also be defined as a water nymph or a siren, living in the rivers of the Amazon Basin.

In the oral tradition of Brazilian folklore, Iara was a beautiful young tribal woman of patriarchal custom who gained admiration from her father, the chief of the tribe, and the others of her tribe for her talent in warfare. However, her praise made her brothers jealous, who decided to kill her stealthily during the night. Iara was skilled enough to defend herself from any sudden attack. But in the course of action, she accidentally killed her brothers. After the incident, she took refuge in the woods to save herself from the wrath of her enraged father. But she was captured and punished by drowning in the river. In some other alternative oral version, she was killed and her body was dumped in the river, blaming the night goddess, Jaci, for her sudden disappearance. Consequently, Iara became a mermaid and vowed to take revenge on men by seducing them and drowning them in the river. According to some folkloric accounts, those who could save their lives, either ended up going crazy or survived with her teeth marks on their neck.

Iara is described in oral Brazilian folklore as a beautiful woman with green eyes, shining greenish hair, light brown or copper-colored skin, and brown eyes, with a fish-like tail who would sit on a rock by the river combing her hair, while basking in the sun. Whenever she becomes aware of the presence of a man around, she starts to sing in her mesmerizing voice to lure the unsuspecting man. She easily seduces the man, and once under her spell, the man agrees, without any hesitation, to leave everything to live with her underwater forever as she is attractive with an abundance of feminine beauty. But as she is immortal, her lovers do age and die, and she becomes sad and alone, recollecting the memory of her happy days until she gets her new lover.

However, Iara is considered to have a dark side too, and any unfortunate death near any water-body or deep in the forest is attributed to her influence. She is blamed for many accidents in the Amazon, especially where men disappear without leaving any trace. It is believed that the thousands who got lost amidst the tropical woods and consequently lost their lives were enchanted by her songs.

She is also held responsible for the hundreds of the destroyed ships. Even today, the native Amazonians are scared of her and avoid to dare water travelling or going near a lake or a river after dusk.

Although the legendary tale of Iara was one of the usual explanations for the disappearance of people who ventured into the heart of the deep forest, Iara or Yara is a very popular female name in Brazil.