Yes, Chem and maf - correct guesses.
Maf, stay a moment
('nie w sosie' is a very weird expression imho)
No, it is not - it goes back to times when people invented the idea of the four humors, or fluid substances: blood, yellow bile, black bile, and phlegm. This theory was closely related to the theory of the four elements: earth, fire, water, and air. E.g., Earth was represented by black bile, fire by yellow bile etc.
In old Poland, humors were also called sauces. Today wa say humor for mood.