Borrowed from Late Latinmnemonicus or its etymonAncient Greekμνημονῐκός(mnēmonikós, “pertaining to memory or remembrance, memorial”) + English-ic(suffix meaning ‘of or pertaining to’ forming adjectives). Mνημονῐκός(Mnēmonikós) is derived from μνήμων(mnḗmōn, “mindful, remembering”) + -ῐκός(-ikós, suffix meaning ‘of or pertaining to’ forming adjectives); while μνήμων(mnḗmōn) is from μνάομαι(mnáomai, “to be mindful, remember”) (from Proto-Indo-European*men-(“to mind; to think”)) + -μων(-mōn, suffix forming adjectives and agent nouns).[1]
Noun sense 1 (“something used to help in remembering a thing”) is borrowed from Latinmnēmonicum(“something used to help in remembering a thing”), from Ancient Greekμνημονικόν(mnēmonikón, “something used to help in remembering a thing”), a noun use of the neuter form of μνημονῐκός(mnēmonikós, adjective): see etymology 1. Noun sense 3 (“synonym of mnemonics”) is borrowed from Late Latinmnemonica, a noun use of the feminine form of mnemonicus: see etymology 1.[1]
2003, Alex Kimbell, chapter 3, in The Unbridgeable Divide: A Love Story, Market Harborough, Leicestershire: Matador, →ISBN, section I, page 54:
Mr Avery was a great believer in mnemonics; he had one for every possible aspect of flying – which was as good a way as any for student pilots to familiarise themselves with their new environment, but unless used on a daily basis could also be dangerous, for there were so many of them.