From Wiktionary, the free dictionary
Borrowed from Korean 오빠 (oppa).
オッパ • (oppa)
- (chiefly in Korean media, women's speech) oppa (elder brother, or an affectionate term of address for a somewhat older man)
- Coordinate terms: ヒョン (hyon), オンニ (onni), ヌナ (nuna), ドンセン (donsen)