Yes, the
Marine motto comes up in my head too. I surprise myself that it doesn't interfere with my enjoyment of the name. "Always faithful" in my mind can apply to more than just the USMC, if I concentrate.
I agree on
Fidelia and
Fidel, and especially
Fidelma. Some books say
Fidelma is related and others give it a separate, Gaelic origin. Either way, I've always liked it. Glad to see there's at least one other out there. :-)