Question: Where does the phrase "hate your guts" (for example "I hate your guts") come from?

I've heard the phrase used as a way to convey extreme and deep dislike of another individual. However, it seems strange to have just been born arbitrarily and I suspect there is a source.

Answer: 
*Guts* is used in many expressions and always refers to something fundamental about a person. These are just [a few](http://idioms.thefreedictionary.com/gut), there are many others:

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> *a gut feeling:* a feeling that you are certain is right, even if you cannot explain why. "My gut feeling was that she was lying."
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> *a gut reaction:* a reaction that is based on your immediate feelings about someone or something "When a tragedy like this happens, I think people's gut reaction is anger and a desire to find someone to blame."
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> *have your guts for garters* (British informal): if you say that you will have someone's guts for garters, you mean that you intend to punish them very severely. "If I catch you smoking again I'll have your guts for garters."
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It's similar to expressions using *stomach* relating to physical ability or courage:

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> I didn't have the stomach to see him, knowing what he'd done.
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Compare:

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> “He which hath no stomach to this fight, Let him depart;" [Shakespeare
>  Henry V]
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and 

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> He had the guts to stand up and say what he thought.
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Just as the heart is the metaphorical seat of emotions, so *guts* are linked to deep, instinctive feelings and reactions. So to say you *hate someone's guts* is to say you hate them to the very core.
I have a theory that the phrase comes from one of the two characteristics of Kosher animals which requires an animal to have more than one stomach. If an animal has non-Kosher-style stomachs (i.e. like a pig) it is not-Kosher (and sometimes seen as not pure). 

Perhaps insulting someone's guts was a way of saying they are like a pig, or other impure animal.