Ruth (רוּת) is the Hebrew name from the Book of Ruth — the Moabite woman who, after her husband's death, refused to leave her mother-in-law Naomi, and made the famous declaration "Whither thou goest, I will go." She became the ancestor of King David.
The Hebrew root means "friend" or "compassion." Ruth has been continuously in the U.S. top 200 since records began. The late U.S.
Ruth 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 Ruth reduce to 4, The Builder. This is a traditional interpretive system, not a factual claim about the name.