Heather is from the Old English hǣð — the purple-flowering shrub Calluna vulgaris that covers the Scottish Highlands and the English moors. The Scottish national flower; white heather is considered lucky (sprigs were carried by Queen Victoria's family).
Featured in countless 1970s-80s American novels and films.
Heather 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 Heather reduce to 2, The Peacemaker. This is a traditional interpretive system, not a factual claim about the name.