I use the elven dictionary in the site's "vault" page as a starting point. I check the maps and existing Audalis stuff - Megilindar for "Bladesinger" is right there on the Maelamin map (southern kingdom).
Others, I google to see if a word speaks to me, or I make it up. K'goth is something like "evil person" combined from words in the elven dictionary I mention. Cora may have been made up entirely, or I may have used the dictionary for referece. I don't remember.
I figure that at worst case, if you make up a word and we hate it, it can be a dialetical variant, local slang term, etc. 
We really ought to compile this stuff into a central location. Maybe I'll edit the first post here and start adding terms we have used in the game there.