Saint Jerome reputedly was the foremost biblical scholar of his day, and he used “Non occides,” in his 4th-Century Vulgate Latin transliteration.
Apparently rabbis, even in Jesus day were moving from murder to just "kill." (I read this somewhere in a scholarly paper, forgotten where). They may of been influenced by the translation of the bible they were reading--namely the Jewish Septuagint.
We need to remember also, that Jerome also used the Septuagint, which is the Greek translation of the older Hebrew text of the Old Testament, done in the ca. 200s BC. So he was translating a translation...not something any translator would do today.
This Greek OT was the common version of the Bible used by Jews and Christians alike in the early centuries of the Church. Jerome translated it into Latin as by his day (ca. 400) people in the western Roman had ceased speaking and reading Greek.
Even certain quotations of the Old Testament in the New Testament in various places have wording that is taken straight from the Greek of the Septuagint--as Greek in the 1st Century would of been more familiar to average Jews, than Hebrew (which of course Gentiles didn't know at all). Hebrew had become a religious language for the Jews at that time--almost like Latin (used to be) in the Roman Catholic Church. Jesus, Paul, and the disciples--scholars are quite sure--used Aramaic (similar to, but not the same as, Hebrew) as their conversational language. Greek was the Roman Empire's common language in the 1st C. though--and anyone slightly educated or involved in commerce, would know it.
There were actually debates among the rabbis in Jesus day, on the proper interpretation of the Hebrew text (not all that different as with Bible scholars today)...as it really was not their first language--and besides, having been written from 400 to 1,400 years before--to their ears must of been archaic (like Middle English is to our ears).
Also, keep in mind that good translators--in trying to understand the best meaning of the old Hebrew, will compare their translation to the Septuagint--since it was older Jewish scholar's understanding of the Hebrew 200+ years before Christ. All I'm saying is the the "thou shalt not kill" issue is not as simple as a mistranslation into English of the Hebrew...
The best scholars today--with many more manuscripts and study aids available though, than even Jerome, AND translating directly from the older Hebrew text, not the Greek translation of the Hebrew, do all agree--the word is closest to the English "murder."