Alva is the Old Norse and Swedish word for "elf" — the supernatural being from Norse mythology. Feminine of Alf.
Alva Myrdal (1902-1986) was the Swedish Nobel Peace Prize laureate, mother of Sissela Bok.
Alva 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 Alva reduce to 9, The Giver. This is a traditional interpretive system, not a factual claim about the name.