Where does “fat” come from?

fat (Swedish) comes from Old Norse fat, from Proto-Germanic fatą, from Proto-Indo-European pod- — vessel, container.

Definitions

Step	Language	Word	Meaning
1	Old Norse	fat	vat, vessel, luggage, clothing; vessel; cover;...
2	Proto-Germanic	fatą	vessel, container
3	Proto-Indo-European	pod-	vessel, container

fat — Etymology, Origin & Word History | Etymology Explorer