돌팔이

Etymology
.

The original sense is possibly archaic, and a folk etymology now claims that the first element is, with the idea that a charlatan is someone who sells stones pretending that they are something else.

Noun

 * 1)  a wandering salesman
 * 2) a charlatan
 * 3)  a medical student drafted as an army physician, who is inexperienced and generally lacks medical expertise