Scarlett began as an English occupational surname for someone who sold or wore scarlet cloth — a rich red fabric that was expensive and prestigious in medieval Europe. The word ultimately derives from the Persian saqirlāt, a richly dyed wool, and travelled west through Arabic and Old French before settling in English.
Today Scarlett sits in the U.S. top 15.
Scarlett 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 Scarlett reduce to 8, The Visionary. This is a traditional interpretive system, not a factual claim about the name.