thingamajig

First recorded in 1870–75; thingum or thingummy + jig ¹, metrically patterned like gobbledygook, rigamarole; thingum perhaps originally from the gradational compound thingum-thangum (based on thing ¹ ) with the same terminal syllable as in crinkum-crankum, harum-scarum, trinkum-trankum, perhaps dog Latin or a facetious alteration of trinkets ( def )