Why do we say, "Oh!" when we are surprised?

Question

I have noticed that I and many of my peers tend to say "Oh!" whenever we are surprised or think of an answer to a question. This "Oh!" is not only prevalent in English, but also in Korean and German. Edit: Sorry for not clarifying. I was wondering why we say, "Oh!" instead of perhaps, "Pft!" or "Tsch!" or any other type of sound.

Answer 1

Hi Asked,

An intriguing issue. Possibly "Oh!" primes the nervous system into tensing the thorax and abdomen in preparation for Fight-or-Flight?

-- Cheers, -- Mr. d.