Hi there, I would like to name a fantasy character with an irish-like name and title/adjective, it should be something like "Niamh the indomitable" but since I was not able to find an irish word for "the indomitable" I tried with something like "the inflexible" and I found "the dolúbtha", is this correct?

There is a way to say "the indomitable" or something similar? The meaning should be appropriate for a "paladin", a true and pure defender of good, his people and such...

Sadly I have at most 19 characters in total to spell the name (name + adjective/title), so I have to pick a moderate long adjective/title.

Can you please help me? (I could have some more names to create in future but this one is enough for now XD)

dochloíte (note the accent í)
(see http://www.teanglann.ie/en/fgb/dochlo%C3%ADte ; http://www.teanglann.ie/en/eid/indomitable)

Niamh Dochloíte (no article necessary in irish)

or docheansaithe (untameable)

Thank you for your help, my character is born
I hope I can have more help for more characters!