vitamin (n.)

1920, originally vitamine (1912) coined by Polish biochemist Casimir Funk (1884-1967), from Latin vita "life" (from PIE root *gwei- "to live") + amine, because they were thought to contain amino acids. The terminal -e formally was stripped off when scientists learned the true nature of the substance; -in was acceptable because it was used for neutral substances of undefined composition. The lettering system of nomenclature (Vitamin A, B, C, etc.) was introduced at the same time (1920).