What does a snake with two legs mean in the eight characters?

According to folk stories, year of the snake was born on the Snake Moon, or year of the snake was born on the Snake Day, or year of the snake was born on the Snake Day. (refers to the eight-character earthly branch, in addition to the annual branch, there are monthly branches, daily branches or time branches. People call the Year of the Loong Moon Dragon born in the Sun Dragon Period a quadruped dragon.

Doesn't mean anything.