When was “Uh huh” invented? is “Uh huh” a formal English?

I am not a native English speaker, i don't understand deeply English language. So i just want to ask you this.

Many years ago, maybe before 2000, i seldom heard English people say “Uh huh”, “Uh huh” when expressing that they are understanding in a conversation. Instead, most people use "ok","ok" to express that they understand what the opposite person is talking.

But now i heard this word every where, they even use this term in country like China & many other countries (I means some Chinese people use "Uh huh" in their conversation is not rare though English is not their language).

I think “Uh huh” in other countries (especially in Asia) is a quite rude expression if u say like that to older people.

So, When was “Uh huh” invented? is “Uh huh” a formal English?

Solution 1:

The OED has it from a 1924 Dialect Notes:

Uh-húh, yes.

But as a part of speech, it will have been used much before that and will be hard to find in print, although I did find an 1858 in the White Cloud Kansas Chief:

"Her name is Peggy ?"

"Uh, huh."

It's often used to acknowledge to a speaker that you're still listening and paying attention, or to answer "yes" to a question.

I'd say it's definitely informal and a simple "yes" or other word should be used in the more formal settings where "uh-huh" may be considered impolite.