Vad heter språket som Orcs pratar?

Ett av deras språk är (drum roll ...) orkish

Orkish was a general term for the jumble of languages used by the Orcs, composed from corrupted borrowings from other languages of Middle-earth. The variations in Orkish between different tribes and types of Orc were so great that it was often useless for communication, and so a standard language was necessary. Sauron devised his Black Speech for this purpose in Mordor, but in practice the Common Tongue was more normally used.

Som du såg, talade de också Svart Tal , vilket var språket bland alla Mordors tjänare, och därmed inkluderade orker. Det skapades av Sauron för att göra orkerna och resten av sina tjänare förstå varandra. När Sauron förstördes (under andra åldern), glömdes den gamla "rena" formen av alla utom Nazgûl.

Språket som användes för inskription på One Ring var "rent" svart tal (JRR Tolkien, Ringens Herre, Ringets Sammanslutning, "Elrondrådet" )

Det svarta talet var åtminstone delvis baserat på Valarin . Det svarta talet var ofullständigt och det fanns inga dikter eller låtar skrivna i den. Tolkien utvecklade inte den lika mycket som de andra språk.

The Black Speech is one of the more fragmentary languages in the novels. Unlike Elvish, Tolkien did not write songs or poems in the Black Speech, apart from the One Ring inscription.

Wikipedia

The Black Speech was not intentionally modeled on any style, but was meant to be self consistent, very different from Elvish, yet organized and expressive, as would be expected of a device of Sauron before his complete corruption. It was evidently an agglutinative language. [...] I have tried to play fair linguistically, and it is meant to have a meaning not be a mere casual group of nasty noises, though an accurate transcription would even nowadays only be printable in the higher and artistically more advanced form of literature. According to my taste such things are best left to Orcs, ancient and modern.

(J.R.R. Tolkien, "Ord, fraser och passager i olika tungor i Ringenes Herre", Parma Eldalemberon 17, s. 11-12.)

För att komplettera @ Shevilaskovics svar: Vanligt användes också, eftersom orker av olika stammar inte kunde förstå varandra, vilket kan ses i avsnittet när Pippin och Merry fångades av orker:

To Pippin's surprise he found that much of the talk was intelligible: many of the Orcs were using ordinary language. Apparently the members of two or three quite different tribes were present, and they could not understand one another's orc-speech. There was an angry debate concerning what they were to do now: which way they were to take and what should be done with the prisoners.