Gail is the English diminutive of Abigail — from the Hebrew Avigayil ("father's joy"). USA Track & Field Hall of Fame (2011). Gail Honeyman — Eleanor Oliphant Is Completely Fine (2017). Gail Halvorsen is male ("Berlin Candy Bomber"). Gail Carson Levine — Ella Enchanted author.
Gail 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 Gail reduce to 2, The Peacemaker. This is a traditional interpretive system, not a factual claim about the name.