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riboflavin (n.)[riboflavin 词源字典]: growth-promoting substance known as vitamin B2, 1935, from German Riboflavin (1935), from comb. form of ribose + flavin, from Latin flavus "yellow" (see blue (1)); so called from its color. Also sometimes known as lactoflavine, as it is found in milk.[riboflavin etymology, riboflavin origin, 英语词源]
thiamin (n.): also thiamine, alternative name for vitamin B1, 1937, coined by U.S. chemist Dr. Robert R. Williams (1886-1965) from thio-, indicating the presence of sulfur, comb. form of Greek theion "sulfur," + amine, indicating the amino group. Or the second element might be from vitamin.