Not to be confused with Shalassi.
Shalassian is the language of the nightborne. It is an offshoot of Darnassian, similar to Thalassian. Ancient nightborne language is so archaic only the oldest elves might be able to read it. 
Nightborne primer (official translations)
Erana-dora isil = A thousand thanks upon you. 
Quel'vala thonos = Nobility through tradition. 
Ru-shanna/Ru shanna shal'dorei = The nightborne will survive.  Tal'ashar = An honor duel. 
Untranslated Nightborne phrases
An'anora = Said by Ly'leth Lunastre when casting a frost trap on her sibling.
An'ratha an'tal-thandros = Said by Warpcaster Thwen when casting a spell in The Drift. 
Anath'ashar = Said by Nightborne mobs when attacking.
Arash-falas = Said by Nightborne mobs upon death.
Ash'tureth denil = Unknown.
Ishnal Toreth = Unknown.
Ith'el kanesh = Said by the Echo of First Arcanist Thalyssra as a greeting. 
Ith'nala kanesh = Said by the Echo of First Arcanist Thalyssra as a farewell. 
Kal'thoras Maldiv = Unknown.
N'eth ana = Said by Chief Telemancer Oculeth when casting a time-stopping spell in his workshop.
Nar'thalas vas manari, thala nar'valas = Said by Thalyssra during a spell to create an empathic bond with Theryn, weaving their arcane essences together, to project his memories as visions. 
Nor'bethos Suramar = Unknown.
Shal'asan torah = Said by Arcanist Valtrois as a greeting.
Shanar daloras = Thalyssra's exclamation as she discovers the Chronomatic Anomaly at the base of the Nightwell.
Tanu'balah = Unknown. Tor'theras Falar = Said by Nightborne mobs upon death.
Something originating from
Suramar is called "Suramari" or "Suramarian".   Though the Shalassian word is unknown, Nightborne do use the term "honored teacher" like the night elves.