And if they don't know Boromir, then throw a box set of the trilogy at their head and never speak to them again. People who don't know the classics are generally not worth associating with, as a rule. [[If you don't like Boromir we can't be friends.
TUTORIAL: How to write in Elvish. This is the most detailed and thorough I've seen. Also, check out a lovely book called "The Languages of Tolkien's Middle Earth". It explains elvish (Sindarian and Quenya), Dwarvish, and others. Written by Ruth S.
Treebeard is Treebeard because his name was too long in Entish for the hobbits to use. And Mount Doom has plenty of names in Lord of the Rings, it's just that Mount Doom was its name in the Common Speech.