Stag question for our British friends

[quigonginger]

No: HPFGUIDX 105776

This has been bugging me, so I'm getting it out and hoping to clear 
it up in my mind.

Being a midwestern US person, I have never heard the word "stag" 
except in reference to "stag parties" (guys getting together to do 
Heaven only knows what) or "going stag" (being without a date).

I was only familiar with the word from reading "the Lion, the Which, 
and the Wardrobe" in which the kids stumble back into England after 
attempting to catch a white stag, which they had hoped would grant 
them wishes.  I had asked what a stag was, and was told it was a deer.

Here in ND, we use 3 words for deer:  1) fawn, a baby deer, 2) doe, a 
female deer, and 3) buck, a male deer.  I'll let you get Julie 
Andrews out of your heads ;-)

So I looked in my American dictionary, and there was quite the 
difference between stag and buck.  

Buck is a male deer or antelope (snip all the other definitions that 
have nothing to do with the topic).

Stag is "a young male red deer...also other various kinds of deer... 
a young unbroken stallion... a male animal castrated after 
maturity...compare to steer..."

Am I reading too much into this?
Is James meant to be "castrated"?
Or "unbroken"?
Or is buck just not commomly used in British vocabulary?

Ginger, who had to ask what Prongs meant, so is probably barking up a 
nonexistant tree here.