The term "merperson" may refer to a Mermaid and a Merman

Mermen are mythical male legendary creatures who are human from the waist up and fish-like from the waist down.

In Finnish mythology, a merman (vetehinen) is often portrayed as a magical, powerful, handsome, bearded man with the tail of a fish. He can cure illnesses, lift curses and brew potions, but he can also cause unintended harm by becoming too curious about human life. A merman, like a mermaid, attracts humans with singing and tones.

A mermaid is a mythological aquatic creature with a human head and torso and the tail of an aquatic animal such as a fish.

Much like sirens, mermaids would sometimes sing to people and gods and enchant them, distracting them from their work and causing them to walk off the deck or run their ships aground. Other stories have them squeezing the life out of drowning men while attempting to rescue them. They are also said to take humans down to their underwater kingdoms.

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