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. top 100 — part of a wave of long, soft, classical names returning to favour.
Adeline reduces to one — the number of originality and quiet independence.