Fionnghal is from the Scottish Gaelic Fionnghal — fionn (fair/white) + gall (stranger/foreigner) — fair stranger, fair foreigner. Fionnghal is one of the Scottish Gaelic feminine names — central to traditional Scottish Highland heritage.
Fionnghal 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 Fionnghal reduce to 5, The Seeker. This is a traditional interpretive system, not a factual claim about the name.