"slit," 1530s, from M.E. chine (with parasitic -k) from O.E. cinu "fissure," related to cinan "to crack, split, gape," from PIE base *gei-, *gi- "to germinate, bloom," connection being in the notion of bursting open.
"a Chinaman," 1901, derogatory, perhaps derived somehow from China, or else from chink (1) with ref. to eye shape.