There are two theories about the etymology of matza (or matzah) מצה.
Some say that it comes from the root נצה - meaning "to hasten", and therefore matza would mean "that which was made in haste." While Klein doesn't mention it, I assume there is a connection to the root אוץ - which also means to hasten, and is the root of such words as מאיץ and תאוצה (acceleration).
The other more popular theory is that matza derives from the root מצץ, meaning "to squeeze, to suck, to drain out". According to this approach, matza receives its name from its dry nature. This root also is the source of the word mitz מיץ - juice, tamtzit תמצית - essence, and mitzui מיצוי - originally squeezing, but later took on a sense of "getting as much as possible out of something". This led to a nice linguistic drasha, that appears here (among other places):
The Hebrew word Matza has the same root as Mitzui (realization of potential), while the Hebrew word Chametz (leaven) has the same root as Hachmatza (missing an opportunity).
As an aside, Onkelos translates matza as פטיר or פטירא (patir or patira). Jastrow explains that term as "free from admixture" - in the case of matza, free of leaven.