Where does “sarrva” come from?

sarrva (Pite Sami) comes from Proto-Samic sërvë, from Proto-Finnic širwe.

Ancestry of “sarrva”, step by step

Step	Language	Word	Meaning
1	Proto-Samic	sërvë	elk, moose, "Alces alces"
2	Proto-Finnic	širwe	—