Adeline is a French diminutive of Adèle, ultimately from the Old Germanic element adal meaning "noble." The same root gives English the words Adele, Adelaide, Adela, and (via Adele) the modern singer's name.
Adeline was popular in the late nineteenth century, faded for most of the twentieth, and has returned strongly in the 2010s. Today it sits in the U.S.
Adeline 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 Adeline reduce to 5, The Seeker. This is a traditional interpretive system, not a factual claim about the name.