In reality, the orcs are named this way in the tongue of men, but in Sindarin they were called Orch. The word Uruk (as in uruk-hai) was related to the word Orc, although it was only used to call high or very strong Orcs, while the lower class of orc was called snaga or slave.
Orcs were breeded first by the dark power in the ancient days and they didn't have a tongue of their own, but they took words from here and there to start their own perverted way of communication and as they grew in number, their lack of organization made them grow in tongues, so most tribes of orcs weren't able to communicate with each other.
Given this, in the third age, orcs used the tongue Oestron as common tongue to organize under Saruman and Sauron. It is said that the black tongue or Oestron was invented by Sauron during the dark years and he attempted to make it the official tongue for anyone who followed him, but to no avail.
