a gadget or other thing for which the speaker does not know or has forgotten the name.
Origin: 1870–75; thingum or thingummy + jig , metrically patterned like gobbledygook , rigamarole; thingum perhaps orig. from the gradational compound thingum-thangum (based on thing ) with the same terminal syllable as in crinkum-crankum , harum-scarum, trinkum-trankum, the ultimately orig. of which is unclear
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