Farrah is from the Arabic farraḥ (فرَّحَ, "joy, gladness") — also a 20th-century English variant of Farah. Her windblown, layered hairstyle — "the Farrah" — was imitated by millions of women in the late 1970s and was on Time magazine's list of the 100 most iconic hairstyles. Farah Diba — last Empress of Iran.
Subject of countless 1970s pop-culture retrospectives.
Farrah 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 Farrah reduce to 7, The Seeker. This is a traditional interpretive system, not a factual claim about the name.