QX4 means something, I just forget what exactly.
Most the "random letter/number" things mean something. All BMW "random letters" are not that at all. First number is the series, 3, 5, 6, 7, etc, and the last two are the engine size. Any numbers that follow are descriptive of the type of engine. i means fuel injected I BELIEVE (remember, BMW's an old company). X was all wheel drive, C convertable, s for sport...etc, etc.
Lexus does the same. the first 2 letters describe the car type, last 3 numbers are engine size. 430 for 4.3 liter, 300 for 3 liter, etc.