doohickey

noun

Etymology: First attested 1914, of uncertain origin, probably from doodad + hickey.

1. A thing (used in a vague way to refer to something whose name one does not know or cannot recall)

   “What does this doohickey do?”

   “Customers will ask for "gizmos" and "what-cha-ma-call-its" and "doohickeys," and make crude drawings on paper bags of what it is they think they need.”