Here's your answer: Homunculus [Huh-muhn-kew-luhs] is the Latin word that translates to "little human" in English. Homunculi (plural) [Huh-muhn-kew-lahy] are said to be humans with extraordinary or abstract skills or bodies. Not like Superman, but closer to monsters in human bodies. Homunculi were used and described in many fictional stories, as well as believed witness tales.
The very first time the word "homunculus" was somewhat described in writing from the times of ancient alchemy studies was between 201-300 AD (3rd century AD) in the text of the Visions of Zosimos. The written material tells of the author Zosimos, who claims encountering a man who commited suicide by stabbing a sword through his body. Zosimos then wrote that the dying man began mutating, and going through what the writer quotes as: "unendurable torment". It was said that the suicidal became "the opposite of himself", which was somewhat like a golem or other frightening beast, but had great intellect and near-human feelings. Later on, the stories tell of Zosimo's meets with multiple homunculi after the first.
Homunculi in the popular anime "Fullmetal Alchemist: Brotherhood" were characterised as immortal souls with a human body. Homunculi are the major antagonists in the series, serving as obstacles for the heroes Edward and Alphonse Elric. The Homunculi are easily distinguished from normal humans because they each posess a red tatoo depicting a dragon-like creature swallowing its own tail, which was called the ouroboros in early alchemy times. It represents the one main concept of alchemy, which was the balance of pair principles. The TV show has showed the creative idea that Homunculi took human bodies when the human has a Philosopher's Stone planted into them. If the human body accepted it, the mysterious aura of the Homunculus would be merged with the human, and the Homunculus would usually take over the human's body (with the exception of Greed). The Homunculi were created by their higher being, whom they call "Father". The Homunculi have varied relationships and attitudes towards each other. But, their feisty consciences lead a few them to treachery, cannibalism, and the annihilation of their own kind.