Where does “sourt” come from?

sourt (Old French) comes from Latin surdus, from Proto-Indo-European swēr- — heavy.

Ancestry of “sourt”, step by step

Step	Language	Word	Meaning
1	Latin	surdus	deaf; inattentive, unresponsive; silent,...
2	Proto-Indo-European	swēr-	heavy

sourt — Etymology, Origin & Word History | Etymology Explorer