Error-correcting code
From Computer History Wiki
An error-correcting code (often given as ECC) refers to a coding system, usually a cyclic redundancy check, which allows errors in data (stored in either main memory or secondary storage) to be automatically detected and repaired.
ECCs are usually only used with stored data, not data in a communication system, since modern networking is designed around the idea of re-sending lost or damaged data (since that simplifies the design of the network).