Munia is from the Old Spanish-Basque muniño (hill, mound). Munia Mayor (c. 990-1066) was the Castilian princess and wife of Sancho III the Great of Navarre — through her, the kingdoms of Castile and Navarre were eventually united in their son Ferdinand I, forming the foundation of medieval Spain.
Sometimes called Mayor of Castile.
Munia does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
In Pythagorean numerology the letters of Munia reduce to 4, The Builder. This is a traditional interpretive system, not a factual claim about the name.