Ummm... Chak, I was just trying to be funny. And I partially disagree with that definition of "thingamajig", having heard and used the term since the 1950s. It refers to an object the correct term for which one either cannot recall at that moment or one does not know. It's a useful shorthand that dates at least to WW2 military, if not before. (I learned it from my WW2 veteran uncle when I was a very young child.) I believe it to be American slang, but it could have emanated from England as well. I have never heard it used in reference to a person.
By the way, it's a "nut" in the sense that it is threaded and the use involves its capacity to fasten two things together.
By the way, it's a "nut" in the sense that it is threaded and the use involves its capacity to fasten two things together.