Where does “pesaing” come from?

pesaing (Indonesian) comes from Indonesian per-, from Malay per-, from Proto-Austronesian *paR- — derivational prefix used to form deverbal nouns.

Ancestry of “pesaing”, step by step

Step	Language	Word	Meaning
1	Indonesian	per-	Used to form nouns from verbs conjugated with...
2	Malay	per-	abstraction, place, goal, result; Used to form...
3	Proto-Austronesian	*paR-	derivational prefix used to form deverbal nouns