After Johann Carl Friedrich Gauss (1777-1855), a German mathematician, physicist and astronomer, discoverer of Bode's Law, the Binomial Theorem and a regular 17-gon. He discovered the prime number theorem while an 18 year-old student and used least-squares (what is called statistical regression in most statistics courses) to predict the position of Ceres.
The word comes from Latin quinque (five) unicia (twelve) and means five twelfths.