Kojima explains the Solid, Liquid and Solidus Snake names

On Twitter, Kojima took some time to explain his reasoning behind the name ‘Snake’, and the three adjectives, ‘Solid’, ‘Liquid’, and ‘Solidus’.

The reason I used Snake as code name in MG was snake was the most appropriate symbol of living thing that hides his presence, & sneaks w/o any noise. The reason I didn’t make any specific snake like cobra, anaconda, viper was because the protagonist is the player. The reason I use SOLID was to give opposite impression of soft image.

Like of all endings of the any series are, the appearance of strongest enemy was a must in MGS. It’s Snake who can surpass the Snake. Thus I brought about “clone”. SOLID vs LIQUID. That is MGS.

As to develop sequel, the 3rd snake was needed. Since both solid & liquid express state, means same true state. Naturally the next would be gas but gas snake is like gas human, not handsome name. So I borrowed from physics terms of “solidus/liquidus”. SOLIDUS is not state but implies the boundary of liquid and solid.

Source: Hideo Kojima Twitter