cough: [14] Although it is largely disguised by the modern English pronunciation, cough is of onomatopoeic origin. It came from a prehistoric Germanic base *kokh- (the kh pronounced not unlike the ch of loch), which initiated the sound of coughing. This has no recorded Old English descendant (although one probably existed, *cohhian), and first appears in the language as Middle English coughen. [cough etymology, cough origin, 英语词源]