Nolwenn

Nolwen or Nolwenn is the result of a phonetic evolution of the two elements Naol and gwenn. Gwenn mutated into Wenn, means "white, blessed" and Naol is a toponym: Noyal-Pontivy, commune located south of Pontivy, Morbihan, hence the global meaning of "the Blanche de Noyal"

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Noyal (-Pontivy) French pen.: ​[nwajal] (Breton: Noal-Pondi)
Noyal is derived from *novio "new" и *ialo- "clearing, cleared place, village"

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https://en.m.wikipedia.org/wiki/Noyal-Pontivy (toponymie)
https://fr.m.wiktionary.org/wiki/Noyal#fr
https://fr.m.wikipedia.org/wiki/Noyal-PontivyNoal-Pondi

According to some sources Nolwenn might indeed mean "white lamb" from Celtic "anoan et gwenn" ("agneau et blanc" in French).
Sources: https://www.prenoms.com/prenom-fille/nolwenn-4055
https://nominis.cef.fr/contenus/prenom/3759/Nolwenn.html
https://fr.m.wikipedia.org/wiki/Nolwen_(pr%C3%A9nom)

There is little to no evidence this name means “white lamb.” While “wenn” means white or pure, the Breton word for lamb is “oan”—not “nol.”

It actually means 'white lamb' in Breton.