Where does “φρένησις” come from?

φρένησις (Ancient Greek) comes from Ancient Greek φρήν, from Proto-Indo-European gʷʰren- — soul, mind; mind; an internal part of the body.

Ancestry of “φρένησις”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	φρήν	The midriff, stomach and lower chest or breast;...
2	Proto-Indo-European	gʷʰren-	soul, mind; mind; an internal part of the body