Ruby comes from the Latin rubeus, meaning "red." The name refers to the red gemstone — a variety of corundum coloured by traces of chromium — long associated in many cultures with passion, vitality, and protection. In Hindu tradition, the ruby is the gem of the sun.
Ruby was popular in the late Victorian era alongside other gem and flower names (Pearl, Opal, Daisy, Violet), faded for most of the twentieth century, then returned strongly in the 2010s. Today it sits in the U.S. top 65 and is in the top 10 in the United Kingdom and Australia.
Ruby 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 Ruby reduce to 3, The Communicator. This is a traditional interpretive system, not a factual claim about the name.