'countermnemonic' is a modern English compound formed from the prefix 'counter-' (meaning 'against') and 'mnemonic' (from Greek 'mnēmonikos', meaning 'of memory').

'counter-' comes via Old French/Latin ('contra') meaning 'against', and 'mnemonic' derives from Greek 'mnēmonikos' and 'mnēmē' ('memory'); the compound 'countermnemonic' is a recent coinage combining these elements in modern English.

As a coined compound, it initially and primarily meant 'something against a memory aid' and has been used to describe aids or cues that impede correct recall; the basic sense has remained consistent.