Hildur is from the Old Norse hildr (battle, warrior). Hildur in Icelandic tradition — one of the most-popular Icelandic feminine names of the modern era; appears throughout Old Norse mythology — Hildr is a Valkyrie of the Poetic Edda (the giver of the eternal battle, the Hjaðningavíg). Hildur Yeoman — Icelandic-American figure. Princess Hildur — Icelandic heritage naming.
and modern film music.
Hildur 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 Hildur reduce to 9, The Giver. This is a traditional interpretive system, not a factual claim about the name.