tonic (n.1)youdaoicibaDictYouDict[tonic 词源字典]
"a tonic medicine," 1799, from tonic (adj.). From 1873 (in gin and tonic) as short for tonic water (1861 as a commercial product, water infused with quinine), so called because held to aid digestion and stimulate appetite.[tonic etymology, tonic origin, 英语词源]