Where does “sís” come from?

sís (Icelandic) comes from English cheese, from English cheesy, from Middle English chesy.

sís (Icelandic): cheese

Definitions

Step	Language	Word	Meaning
1	English	cheese	A dairy product made from curdled or cultured...
2	English	cheesy	Overdramatic, excessively emotional or clichéd,...
3	Middle English	chesy	—

sís — Etymology, Origin & Word History | Etymology Explorer