How is it even possible? Haven't you ever wondered?
I'm making my money - at least part of it - by translation, or, more precisely, adaptation of commercial ads, and I'm still wondering.
Even the simplest, most common words have different etymologies in different languages.
For example, English "letter" (as graphical symbol) comes from similar words in french and letter that has possibly originated from greek "diphthera" - "tablet," with change of d- to l-. Very early on it is tied with written documents, e.g. letters. (Source here.)
In Latvian, "letter" is "burts", which has originated from a family of words with meaning "to conjure", "to do magic"; it can actually be translated as "conjured" in specific cases. We do not think of it every day, very likely most of language users aren't aware of this double meaning, but the meaning is there. Our name for letter as a document is "vēstule", which basically means "message" (we have name "vēsts" for messages that aren't necessarily written in a letter format).
And this is just a simple word, easy to translate. This blog entry by Louise Marley prompted me to look up name "werewolf". In English it doesn't actually mean "was a wolf". As i found out in Wikipedia, the name "most likely derives from Old English wer (or were) and wulf. The first part, wer, translates as "man" (in the sense of male human, not the race of humanity)." In Latvian, it's a similar, maybe a wee bit more poetic "vilkacis" which means "wolf-eyes" (curiously enough, the tradition states that it has human eyes in its wolf form). But in Russian, the general term for werewolf is "о́боротень" or "перевёртыш" which means "the one turning/changing into something" and thus not implying the wolf form as necessary.
The majority of words have similar discrepancies in meanings - not even mentioning the sound of these words that is important in perception too, as well as common usage of these words. If you have a slight discrepancy in every word you translate, how is it possible to convey the meaning of text from one language to another? (And it is possible, I've seen it, and it still strikes me as miracle.)