Thingumbob

Part of speech: noun

Definitions

1. An object or gadget whose name you cannot recall or do not know
2. Something whose actual name escapes you or remains unknown to you
3. A device or item for which you have forgotten or never learned the proper designation

Etymology: Speakers reach for "thingumbob" when a name slips away, and the word is built the way many placeholder words are: "thing" with a playful, nonsensical ending tacked on. Its final syllables have no traceable source word, which fits its purpose. The ending seems to be sound-play, the same impulse behind "hocus-pocus" and "higgledy-piggledy," though the exact model is uncertain. Its relatives show the same pattern. "Thingummy" is a close variant, "thingamajig" is the American cousin, and "whatchamacallit" builds the same vague reference from a question. In each case the speaker stands in for a name they cannot produce, and the playful sound makes the gap feel less awkward.

Synonyms: gadget, gizmo, contraption, doohickey