Here's another linguistic anomaly:Ambient and Ambiance.
We had a discussion at the Mindles the other day about this one. I happened to say that candle light created a certain ambiance - I pronounced it 
(AM-be-ence). I was savaged for pronouncing it incorrectly, with my wife saying "What, have you become American now?!" I was informed that the correct pronunciation was (AHM-be-ahnce). I was aware of this but I defended my pronunciation by saying that the word is derived from "ambient", which is pronounced (am-BE-ent) and therefore (AM-be-ence) should be a correct pronunciation. It was suggested that "ambient" could be pronounced (ahm-be-AHNT). I hadn't heard it pronounced this way before. Of course, I then countered myself by saying well they both derive from the French "ambiant", so why shouldn't they both be pronounced with that "ah" sound, instead of the flat "a"?
Well being the linguistic dork that I am, I had to research it. The results are actually rather interesting.
Ambiance:
There are two correct pronunciations for this word. (AM-be-ence) and (AHM-be-ahnce) are both accepted pronunciations according to Collins and the American Heritage Dictionary.
Here's why. There are two acceptable spellings! It can either be Ambience or Ambiance - who knew?!
Ambient:
There is only one correct pronunciation of this word - (am-BE-ent), again according to both Collins and the American Heritage Dictionary.
But why?
Because they have two different roots. I assumed that both words came from the French "ambiant" which means "surrounding" - I was wrong. Only "ambiance" comes from the French "ambiant", hence it's French pronunciation. "Ambient" comes from the LATIN "ambient" which is the present participle of "ambre" which means "to surround, as well as "ambi" which means "to go." Of course they both ORIGINALLY came from the Latin, so you might think that "ambient" is just the adjective of "ambience". That is how it was formed in the nineteenth century, but the two words have diverged enough that their associations and pronunciations are different.
So with a little research, I managed to confuse myself even more, by dismissing my previously held notion that if two words have the same root, they must be pronounced the same. Not so. Wait........they DON'T have the same root, that's what I just spent the last hour researching.
As Mike so aptly pointed out, "Language doesn't make any sense."