From earlier *peq. Probably onomatopoeic, but compare also Manchu ᡶᡳᠣᡥᠠ (fioha, “chick”), Middle Korean 비〮육 (píyùk, “chick”) and Japanese 雛(ひよこ) (hiyoko, “chick”).
пʼеӄ (pʼeq)
