Tegan is the Welsh word for "fair" or "beautiful" — from teg (fair). Used as a feminine name in Wales.
Tegan and Sara (Tegan Quin, born 1980) is the Canadian indie duo.
Tegan 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 Tegan reduce to 2, The Peacemaker. This is a traditional interpretive system, not a factual claim about the name.