Meredith comes from the Old Welsh Maredudd — composed of mawr (great) and iudd (lord) — meaning "great lord" or "great ruler." It was originally a male Welsh name; in modern English use it is predominantly female.
Meredith has been continuously in the U.S. top 500 since the 1950s. The character Meredith Grey on Grey's Anatomy (2005 onward) has kept the name in popular memory for two decades. Today it sits in the U.S. top 600.
Meredith 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 Meredith reduce to 1, The Leader. This is a traditional interpretive system, not a factual claim about the name.