"aiding the memory," 1753, back-formation from mnemonics, or from Greek mnemonikos "of or pertaining to memory," from mnemon (genitive mnemonos) "remembering, mindful," from memne "memory, a remembrance, record, an epitaph; memory as a mental faculty," from base of mnasthai "remember," from PIE root *men- "to think" (see mind (n.)). The noun meaning "mnemonic device" is from 1858. Related: Mnemonical (1660s).
mnemonic mne·mon·ic (nĭ-mŏn'ĭk)
Relating to, assisting, or intended to assist the memory. n.
A device, such as a formula or rhyme, used as an aid in remembering.