A fundi is a person who knows what they are doing. They are a specialist, a person in the know, a learned person.
Both Ndebele (or Zulu) and Swahili are part of the Bantu language family and while they are considerably different to the point that a speaker of one can't be easily understood by a speaker of the other, they share many similar word roots, kind of like French and Spanish.
For example, to say "I want to learn Swahili" in kiSwahili you could say:
Nataka kujifunza kiSwahili
where kujifunza is the infinitive "to learn." "Ku" is the infinitive prefix and the root is "-fun(z)-" pronounced basically "foonz." To say "I want to learn Ndebele" in Ndebele, you'd say:
Ngifuna ukufunda isiNdebele
Where "uku" is the infinitive prefix, pronounced differently from the ku in Swahili. In Ndebele it's pronounced "ugoo," but the root is similar. "Funda" versus "funza." Similar things happen in all the Bantu languages. In the house now we have Zulu speakers, Ndebele speakers, Siswati speakers and kiSwahili speakers and each has its little details like this.
Anyway, a fundi is a 'learn-ed one" and when you need something handled in Eastern Africa, you call one. While we've been here we've needed fundis for plumbing, electricity, and sewing.
My wife went and bought some cloth and got measured to have a fundi make her a series of dresses. He was a very kind, genteel man who has a genuine interest in fashion and his little one-room shop was plastered with patterns and designs. Most fundis have been doing whatever they've been doing for a number of years, otherwise they'd be an amateur. You do have to keep on your guard because, unlike the states, there's no guarantee for the work. For example, we had a plumber who did some work for us, and while it was a flat fee, when we found the work to be unacceptable the next day, our only recourse was to either pay the same guy again, or find another who could fix the previous guy's screwup. It's an interesting system largely based on word of mouth, reputation and who's got the tools.