Where does “巴生” come from?

巴生 (Chinese) comes from Malay pasang, from Proto-Malayo-Polynesian *pasaŋ.

Ancestry of “巴生”, step by step

Step	Language	Word	Meaning
1	Malay	pasang	to rise; couple
2	Proto-Malayo-Polynesian	*pasaŋ	—