Whatchamacallem

Part of speech: noun

Definitions

1. A colloquial stand-in for a person whose name the speaker has forgotten or does not know
2. Used in casual speech to refer to someone whose name has slipped one's mind at the moment
3. An informal placeholder word for a person whose name is unknown or temporarily forgotten

Etymology: "Whatchamacallem" is a fusion of the phrase "what you may call them," squeezed together until it became a single word. The process is called univerbation, meaning a run of separate words gradually hardens into one, and the contraction shortened the phrase further by dropping sounds from its middle. Speakers used it as a stand-in when they could not recall or did not bother to name a person, so the word works the way "thingamajig" does for objects, filling the gap where a name should be.