This looks like a job for our Greek resident, PriaposLovs, but I'll take a swing at it and he can make any necessary corrections later. :)
"Leuretha" may mean "Brightest and Best". I say that, because "Leukos" is a Greek combining form meaning "white, bright", and "
Aretha" or "
Retha" is a Greek name being "The Best".
Anyone else here have any other theories on this name (which appears to be a modern invention)?
--
Nanaea