riboflavin (n.)youdaoicibaDictYouDict
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.
thiamin (n.)youdaoicibaDictYouDict
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.