Qin shi huang's name means "commencing emperor" or "first emperor." why was he called that name when the xia, shang, and zhou dynasties were far older?

Qin Shi Huang was called "Commencing Emperor" or "First Emperor.", because he succeed the introduction of Legalism, and was the Emperor of all the territory of China, a remarkable feat., which  China unification has endured for more than two thousand years.

He also had gigantic projects, including the first version of the Great Wall of China.