Where does “ng- -in” come from?

ng- -in (Indonesian) comes from Indonesian -in, from Betawi -in, from Balinese -in.

Ancestry of “ng- -in”, step by step

Step	Language	Word	Meaning
1	Indonesian	-in	used to form benefactive aspect
2	Betawi	-in	used to transitivize a verb
3	Balinese	-in	—