carb (n.)

general name for a group of organic compounds consisting of carbon atoms in multiples of 6 and hydrogen and oxygen in the proportion of water, 1851, from carbo-, combining form of carbon, + hydrate (n.), denoting compound produced when certain substances combine with water, from Greek hydor "water" (from suffixed form of PIE root *wed- (1) "water; wet").

The name carbohydrate was given to these compounds because, in composition, they are apparently hydrates of carbon. In structure, however, they are far more complex. [Flood]