Where does “Се̄са” come from?

Се̄са (Orok) comes from Ainu シサㇺ, from Japanese シ.

Ancestry of “Се̄са”, step by step

StepLanguageWordMeaning
1Ainuシサㇺforeigner, non-Ainu
2Japaneseシ—
Every word from Japanese シ →Every word from Ainu シサㇺ →