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In battle you kill and you sweat because your blood gets warm - physical exercise. Killing someone in Battle was acceptable unless you were on the losing end - then you may be killed in Cold Blood.
If you were plotting, scheming whatever someones death you were not worked up in the heat of the moment/battle your blood was cold. So cold blooded was the term.
Aramaic texts of the Bible state thou shall not commit murder. Murder was defined as the unjustified taking of a life. If the killing was justified as in an execution it was not murder. If it was mot justified it was cold blooded murder. Manslaughter was a lesser crime BTW
Look to Byzantine, Old English, and Latin for your contexts. Christian, Muslim, and Jewish all held to these standards in the early days. The Koran states very similar if read in Arabic. Since I cannot read Hebrew I have to depend on English translations of texts.
Today we have a semantic wars going on and the definitions are all goofy. Look to English common Law for your eveidence here