the tengku's lost language

The tengku are very good at assimilating into other cultures and can learn new languages very fast.  They will adapt to any culture but during the the Second Age they mostly attached themselves to elven nations and communities and during the the Third Age they have mostly attached themselves to human nations and communities.   In some ways, they were too good at assimilating to other cultures.  During the Second Age, most tengku spoke Elven more often than their own tongue only speaking their own tongue in private.  While tengku are highly literate compared to most other races, they almost never wrote in their own language.   Tengku made a point to teach their language to their young to keep it alive, but the language still declined over the Second Age.  Overtime from disuse the tengku probably lost 10-20% of their languages words via lack of use.   During the Second Unmaking, most tengku that survived only managed to survive by closely tying themselves to enclaves other other races.  When survival was the prime concern during the Second Unmaking and the Red Era, it was less of a priority to teach tengku chicks their mother tongue when teaching them Elven and Common  will help keep them alive.   During the current Feudal Era, the tengku work fiercely to teach their young their native language but by this point, only about 30% of their original words are left in their collective memory.   Their grammar is pretty much forgotten too, most tengku will splice their own language into the framework of Elven or Common grammar.