Blerta is from the Albanian blertë — green, verdant (springtime green). Blerta is one of the Albanian + Kosovar feminine nature names — central to traditional Albanian seasonal-naming heritage.
Blerta 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 Blerta reduce to 4, The Builder. This is a traditional interpretive system, not a factual claim about the name.