Latin phrases adopting an imprecise/incorrect meaning in English (or other languages)

Question

Before staring learning Latin, I was already acquainted with many Latin expressions accommodated to Spanish (and English). Typical examples are ex ante, ex post, vice versa, et cetera, etc.

Now that I've started to learn Latin, I can dig deeper into the meaning of these expression in its original language. But the agreement seems sometimes not to be literal. There is already an example here. Another example, so far as I can tell, is vice versa. For instance, in the Vulgata we read (Esther 9:1):

Igitur duodecimi mensis, quem Adar vocari ante jam diximus, tertiadecima die, quando cunctis Judaeis interfectio parabatur, et hostes eorum inhiabant sanguini, versa vice Judaei superiores esse coeperunt, et se de adversariis vindicare.

But as far as I can understand, the meaning there is not that which we normally understand to be vice versa in English (or Spanish). There is a turn of things, but I don't see a literal translation being valid there.

There are of course plenty of examples where the meaning is mostly if not equally identical, e.g. viva voce, vox populi.

I would like to know (i) if discrepancies is actually a common phenomenon, and if so, (ii) why does it occur. Is it because of the increasing Latin illiteracy of an important group of the population, such that at some point the users of an expression no longer understand the language behind it, giving further way to imprecise, if not directly incorrect meanings? (Not that there is necessarily something wrong with this)

Answer 1

The short and unsatisfying answer to this is that languages, by nature, are subject to change.

Latin words or whole phrases entered the English language via lexical change (i.e, the introduction of new words or phrases) in most or all cases, with their meanings relatively unchanged. These introduced words and phrases often then, either through popular adoption or other means, undergo semantic change (i.e, a change in meaning).

With regards to Latin loanwords or loan phrases, the specific change they undergo is widening, the inclusion of additional meanings or usages to a term. There are many things that can cause this widening and I do not have enough of a background in historical linguistics to answer what those things might be. That said, however, you can read more about the potential causes of semantic change here.