What does 별주부 (鱉主簿) literally mean?

 ANSWER: the Snapping Turtle Herbalist

The word 별주부 (鼈主簿) can translate as "snapping turtle" (자라), but it literally means "The Snapping Turtle (鼈) Herbalist (主簿)." An herbalist is someone who uses plants to make "herbal medicines," which were commonly used to treat various illnesses in old Korea and are still used in Korea today. So, in old Korea, an herbalist was essentially a doctor. Korean doctors also used the organs of animals to make tonics and medicines.

The word 별주부 comes from an old Korean fable entitled 별주부전, which can translate as "The Tale of the Snapping Turtle Herbalist." The story is also referred to as 토끼전, which can translate as "The Tale of the Rabbit." Here is my summary of the story:

The Dragon King of the South Sea (남해의 용왕) gets sick and none of the medicines in his sea kingdom can cure his illness. It seems the Dragon King may even die. After praying to Heaven for a cure, a supernatural being (신선) comes down and tells the Dragon King that he can cure his illness by eating the hot liver of a rabbit, which means the rabbit would have to be alive just before the Dragon King eats its liver. However, the rabbit is a land animal, so since the Dragon King, who has lived under the sea all of his life, does not know what a rabbit looks like, the supernatural being describes what a rabbit looks like and then disappears. 

When the Dragon King asks for a volunteer to go on land to capture a rabbit for him, at first no one steps forward, but then the Snapping Turtle Herbalist says he will go if he has a drawing of what a rabbit looks like. The Dragon King orders the abalone (전복) to describe a rabbit while the royal artist draws a picture of one based on the description. The Snapping Turtle Herbalist then takes the drawing and leaves the sea kingdom to go find a rabbit on land. 

Once on land, the Snapping Turtle Herbalist meets a fresh-water turtle (남생이) who points him in the direction he should go to find a rabbit. The Snapping Turtle Herbalist eventually finds a rabbit and tricks it into going back with him to the sea kingdom of the Dragon King. When the rabbit gets to the sea kingdom and realizes that the Dragon King is about to cut open his belly and eat his liver, the rabbit lies and says that he had taken out his liver and left it on land before coming to the sea kingdom, but says he is willing to go back and get it. The Dragon King believes him and lets him go back to land with the Snapping Turtle Herbalist. 

Once safely back on land, the rabbit angrily chides the the Snapping Turtle Herbalist, saying, "How could I walk around without a liver, you dummy? "If you want to take something back to the Dragon King, take this rabbit poop. It is supposed to be good medicine." 

The Snapping Turtle Herbalist has no other choice but to take the rabbit poop back to the Dragon King, who eats it and is miraculously cured.

The above version of the story may be slightly different from other versions, but it is based on the Korean language one I read.

In the following Korean video, a woman tells the story of the Snapping Turtle Herbalist, using lots of interesting pictures and explanations, but she talks pretty fast.