Megara (Μεγάρα) was the Theban princess and first wife of Heracles — daughter of King Creon. In Greek tragedy, her tragic fate at Heracles's hands is one of his most haunting episodes.
Megara 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 Megara reduce to 9, The Giver. This is a traditional interpretive system, not a factual claim about the name.