'noncarbohydrate' is formed by the prefix 'non-' (from Latin 'non', meaning 'not') attached to 'carbohydrate' (the chemical term for compounds related to sugars).

'carbohydrate' originally appeared as phrases like 'hydrate of carbon' (French 'hydrate de carbone') and as German 'Kohlenhydrate'; the modern compound 'carbohydrate' developed in the 19th century. The negative prefix 'non-' was later attached to create 'noncarbohydrate' to denote substances that are not carbohydrates.

Originally 'carbohydrate' referred to 'a hydrate of carbon' (a descriptive chemical notion); over time it became the standard term for sugars, starches, and related molecules. 'Noncarbohydrate' consequently came to mean 'not belonging to that class' in scientific and general usage.