Fosetta is not listed in my Italian name dictionary (
Santi e Fanti by
Enzo La
Stella T.).
In my experience Moselle has sometimes been used as a feminine form of
Moses in Jewish American families, so I don't think it's always a working class name.
Although I don't know for sure, I would strongly suspect that
Nadira is used by Christians in Arabic-speaking countries as well as Muslims, and it is certainly used by non-Muslim African-Americans in the USA.
I have yet to see any name from an African language that seems to me to be a candidate for the origin of
Keisha. "Kisa" is a name meaning "kindness" in the Ganda language of Uganda, but that is probably a coincidence. Keshawna is almost certainly a recent creation because it fits in with Lashawna, Rashawnda, Tyshawn, etc. and other African-American creations based on
Shawn.
From a quick bit of Googling, the main references to a woman named Saffi are to Saffi
Crawford, a writer of books on astrology and numerology who lives in
London. My guess (though it's only a guess) is that Saffi is more likely to be a pet form of
Saffron than a form of
Sophie in her case. Saffi is also an alternate spelling for the city of
Safi in Morrocco, is used as a surname in Arabic speaking countries, and turns up as the name of a male Jewish singer, though that may just be a stage name. It certainly could be a pet form of several Arabic girls' names such as Saffanah, Safa, and Safiyah. The Arabic name Safiyah is not a form of
Sophia but goes back to words that meant "sincere friend", according to
Digest of Muslim Names by Fatimah
Suzanne Al Ja'fari.