1910, American English, perhaps an alteration of gimcrack, or an anagram of magic.
In a hotel at Muscatine, Iowa, the other day I twisted the gimmick attached to the radiator, with the intention of having some heat in my Nova Zemblan booth. [Domestic Engineering, Jan. 8, 1910]
-y 2
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy). Adjectives such as hugy, vasty are artificial words that exist for the sake of poetical metrics.