Where does “ventrālis” come from?

ventrālis (Latin) comes from Latin venter, from Proto-Indo-European wend-tri.

Ancestry of “ventrālis”, step by step

Step	Language	Word	Meaning
1	Latin	venter	belly, abdomen; body, trunk; stomach
2	Proto-Indo-European	wend-tri	—

ventrālis — Etymology, Origin & Word History | Etymology Explorer