Where does “膎汁” come from?

膎汁 (Hainanese) comes from Indonesian kecap, from Hokkien 膎汁.

Ancestry of “膎汁”, step by step

Step	Language	Word	Meaning
1	Indonesian	kecap	soy sauce; sound of tongue smacking
2	Hokkien	膎汁	—

膎汁 — Etymology, Origin & Word History | Etymology Explorer