The Prim'ta was the ceremony of implanting a larval Goa'uld in a young Jaffa. Prim'ta was also the word that referred to the larval Goa'uld itself. The ceremony marked a Jaffa's coming of age, and the beginning of their warrior training. While a prim'ta biologically requires a human vessel, they are incapable of effectively controlling the host. It was also the way the Goa'uld insured that the Jaffa were forever tied to them, as the prim'ta effectively functioned as the Jaffa's immune system. The first prim'ta ceremony took place on the planet Dakara. (SG1: "Children of the Gods", "The Enemy Within", "Bloodlines", "Bane", "Reckoning, Part 1")
Possible Etymology (non-canon)
It is possible that prim'ta is a compound word made up of Latin word fragment prim (like in primitive or primal) and the Chinese word ta (它), a word which today means "it" but in ancient times meant "snake".