For example, you can upset the apple cart–which means you tipped it over and all the apples spilled everywere.

Since upset can also mean “make a mess of something by jostling it or other means…” (definition mine) there is no personification involved.

I think its rather the opposite. The word didnt always mean “angry, emotional”–it just meant accidentally disordered.

“Angry stomach” would be personification.

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The stomach is not a full person, so it can’t experience emotions like a person.

To call a stomach “upset” is to give it the characteristics of a full person, which is personification.

But ina book about body parts, where the foot just kicked the stomach, you could speak of an ‘upset stomach’ personified.

no,this term isn’t personification as ‘upset’ here doesn’t signify ‘sadness’. the quality or feeling of sadness hasn’t been given to stomach. its just a term which means you are not well