Where does “ngokuba” come from?

ngokuba (Zulu) comes from Zulu ba, from Proto-Bantu -báa — to be; to dwell; to become.

Ancestry of “ngokuba”, step by step

Step	Language	Word	Meaning
1	Zulu	ba	to be; to become
2	Proto-Bantu	-báa	to be; to dwell; to become