Meaning of thingum in English:

thingum

Pronunciation /ˈθɪŋəm/

noun

(also thingam)
informal
  • = "thingummy". In early use (with reference to a person) also "Mr Thingum".

Origin

Mid 17th century (in an earlier sense). Apparently an extended form of thing, perhaps after Latin nouns in -um or (accusative forms in) -am.