どっち？

Derived from '何方' (dochira), an older and more formal word for 'which one'. 'どっち' is a contraction and a more colloquial form. The 'ど' (do) indicates an interrogative, similar to 'どれ' (dore - which one among many) or 'どこ' (doko - where). The suffix 'っち' (-cchi) is an informal, somewhat childlike or familiar ending often used in contractions or nicknames in Japanese. Its usage became widespread in modern Japanese to simplify speech in casual contexts.