I thought it would be really weird to say "ouch" when you accidentally stumble or hurt yourself - it felt completely unnatural. It was fascinating that different cultures have such different exclamations for pain!
Well it turns out that it's not the case. Humans all make roughly the same sound when they stub their toe, it's just that different countries write it down differently and think of it slightly differently.
I think "Huh" is similar. A "Confused grunt" noise is approximately similar in most of the world, but different languages write it down differently.
"Yet many world languages contain a separate set of words that defies this principle. Known as ideophones, they are considered to be especially vivid and evocative of sensual experiences. Crucially, you do not need to know the language to grasp a hint of their meaning. Studies show that participants lacking any prior knowledge of Japanese, for example, often guess the meanings of the above words better than chance alone would allow. For many people, nurunuru really does feel ‘slimy’; wakuwaku evokes excitement, and kurukuru conjures visions of circular rather than vertical motion. That should simply not be possible, if the sound-meaning relationship was indeed arbitrary."
The same happens with animal noises. The sound is the same, just different languages write it down differently. For instance, English "woof woof!" and Polish "hau hau!" look completely different, but there is an overlap in possible pronunciations, and that point of overlap actually does resemble the sound dogs make.
"Ouch" is what you say to express that you imagine something hurt, what people actually say is more like "ow" or "argh".
No idea how to explain the pronunciation though ...
Here's a French speaker pronouncing it: https://youtu.be/Dtta-mW6Pro?t=15