On trying to find the pronunciation of the name of Mizero Ncuti Gatwa, a Rwandan-Scottish actor who will be playing the Fourteenth Doctor, I noticed the NC pairing and its pronunciation is listed on Wikipedia as ʃ. I then wondered what the origin of the orthography was.
But that doesn't explain how NC came to represent the sound that in English is most often spelt with SH. Is the N silent at least to English speakers, and part of a Swahili-esque noun class? N- is class 9/10 'animals, 'other', loanwords' according to Wikipedia.
Where does the orthography come from?