Place and people-group names

I'm building a First Age-based world for a game and trying to name a secret stronghold and the group of people who live there in Sindarin. The secret stronghold is supposed to hold my big bad evil guy until he changes his ways. Based on Quirinius's previous answer (www.elfdict.com) I'm thinking of naming the fortress Echerios (City of Repentance) and the people would be the Cundolomba (the Secret Guardians). I know nothing about grammar and I'm sure I've messed something up... can someone please look over these names and correct them, or suggest better ones? Thanks!

Regarding "Echerios," I believe you missed the 't,' so it should be "Echeriost" or "Ederiost." I would lean towards "Ederiost" myself.

Regarding "Cundolomba," that is not correct for Sindarin as it appears you are using Quenya elements.

In Sindarin, "Cund" means “Prince.” Perhaps "Haldirrim" would work for you, using the Noldorin hall “hidden” and √TIR “guard,” plus "-rim."

Note that it could also be mistaken for "Hidden Hero people" as well. eldamo.org