Hildegard combines the Old German hild (battle) and gard (enclosure, protection) — meaning "battle protector." Saint Hildegard of Bingen (1098-1179) was the Benedictine abbess, mystic, composer, and polymath — Doctor of the Church.
Hildegard is widely used in German Catholic families.
Hildegard is a compound name. Its parts are hild + gard — each an attested element with a recorded meaning of its own.
Hildegard 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 Hildegard reduce to 5, The Seeker. This is a traditional interpretive system, not a factual claim about the name.