Where does “Perse” come from?

Perse comes from Old French Piers, which derives from Old French Pierre, a name of uncertain ultimate origin.

Ancestry of “Perse”, step by step

Step	Language	Word	Meaning
1	Middle English	pers	blue, blue-grey; blue cloth; blue, bluish
2	Old French	pers	twelve peers
3	Medieval Latin	persus	Persian
4	Latin	Persicus	Persian
5	Ancient Greek	περσικός	—
6	Ancient Greek	Πέρσης	a Persian
7	Old Persian	𐎱𐎠𐎼𐎿	a Persian
8	Proto-Iranian	párcuš	rib
9	Proto-Indo-Iranian	párćuš	rib
10	Proto-Indo-European	pérḱus	chest; rib