Boringly:
Kermario means 'Place of Death' (although the 'ker' bit, as we all know, probably has many more meanings). The 'mario' bit I guess has connections with words like mort and stuff.
Manio, I'm totally guessing, probably has something to do with Maen or Men which is Breton for 'stone'.
As for 'Kerluigi' I'm stumped...