Explain the origin of the magnitude designation for determining the brightness of stars. Why does it seem to go backward, with smaller numbers indicating brighter stars?

Hipparchus was an ancient Greek who classified stars based on the brightness in 129 B. C. He grouped the brightest stars and ranked them 1 (first magnitude) and dimmest stars as 6 (sixth magnitude). Thus, the smaller numbers indicated brighter stars. Now, the scale extends in negative axis as well. More the negative number, brighter is the star. For example, Sun has magnitude - 26.74.

This the apparent magnitude which means the classification is based on the brightness of the star as it appears from the Earth.