thingummy

noun

Etymology: From thingum + -y. Compare thingamabob and thingamajig.

1. Synonym of thingy: something one cannot remember the name of, or is unable to or does not care to specify precisely.
2. Synonym of whatshisname: someone one cannot remember the name of.

   “Once, in his first term, Cartwright had been bold enough to ask him why he was so clever, […] ‘It’s memory, Cartwright, old dear. Memory, the mother of the Muses . . . at least that’s what thingummy said.’ ‘Who?’ ‘You know, what’s his name, Greek poet chap. Wrote the Theogony . . . what was he called? Begins with an “H”.’ ‘Homer?’ ‘No, dear. Not Homer, the other one. No, it’s gone. Anyway. Memory, that’s the key.’”