I don't know if there can be another origin, but in a Hispanic context, Miluka is a respelling of Miluca, a nickname of Milagros, through the short form Mila plus the diminutive suffix -uca, also found in other nicknames (Pilar>Piluca, María>Mariuca, Ana>Anuca). Since Mila is also used sometimes as nickname of Emilia or other names, Miluca could be a nickname of those names.
Lumia
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