Median means middle. When a strip of grass divides one direction of a highway from another, it's called a median because it runs through the middle.
Median comes from the Latin word medius, which also means middle. In math, the median is a number in the middle of a list. In the set 2, 3, 5, 10, 25, the median is 5. The statistical median is often linked to the idea of an average. A town's average income might seem high if there are two extremely rich people who live there. The median will tell you the income of the person halfway through the list.