The scholar Alexandre Nemirovski, on linguistic evidence, has proposed that Tolkien based it on the ancient Hurrian language, which like the Black Speech was agglutinative.
Unlike his extensive work on the Elvish languages, Tolkien did not write songs or poems in the Black Speech, apart from the One Ring inscription.
The Black Speech was not intentionally modelled 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.
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.
Because the Black Speech in general is an accursed language, and the Ring inscription in particular is a vile spell, Tolkien never drank out of the goblet, and used it only as an ashtray.
[3] The linguist and Tolkien scholar Carl F. Hostetter wrote that the Dark Lord Sauron created the Black Speech "in a perverse antiparallel of Aulë's creation of Khuzdul for the Dwarves".
[4] Sauron attempted to impose Black Speech as the official language of the lands he dominated and all his servants, but in this he was only partially successful.
[15] The Swedish linguist Nils-Lennart Johannesson compared the phonology and syllable structure of the Black Speech with those of Tolkien's two major Elvish languages, Quenya and Sindarin.
He stated that as the only language of this type in Middle-earth, this made the Black Speech more important than it would appear from the few words Tolkien defined for it.
For instance, the word for Orcs, the monsters made in mockery of the Elves, is Quenya "urco, orco", which becomes Black Speech "Uruk".
[19] The linguist Joanna Podhorodecka examines the lámatyáve, a Quenya term for "phonetic fitness", of Tolkien's constructed languages.
She notes that Tolkien's inspiration was "primarily linguistic"; and that he had invented the stories "to provide a world for the languages", which in turn were "agreeable to [his] personal aesthetic".
[23] Mark Mandel, writing in the Tolkien Journal in 1965, wrote that -ishi is "a postposition of location, or (to borrow a term from Finnish grammar) an inessive suffix.