Where does “Fars” come from?

Fars (English) comes from Persian فارس, from Arabic فَارِس, from Middle Persian 𐭯𐭠𐭥𐭮𐭩, from Old Persian 𐎱𐎠𐎼𐎿, from Proto-Iranian párcuš, from Proto-Indo-Iranian párćuš, from Proto-Indo-European pérḱus — chest; rib.

Ancestry of “Fars”, step by step

StepLanguageWordMeaning
1PersianفارسPersian; a Persian; horseman, rider
2Arabicفَارِسthe knight
3Middle Persian𐭯𐭠𐭥𐭮𐭩Persia
4Old Persian𐎱𐎠𐎼𐎿a Persian
5Proto-Iranianpárcušrib
6Proto-Indo-Iranianpárćušrib
7Proto-Indo-Europeanpérḱuschest; rib
Every word from Proto-Indo-European pérḱus →Every word from Proto-Indo-Iranian párćuš →Every word from Proto-Iranian párcuš →