Earlier this year, Infiniti switched it's naming scheme so that all of its cars are called either Q[number] or QX[number]. A lot of people thought it was pretty odd, and I even had a conversation with a friend who was considering "an Infiniti QX" in which I never figured out which car she meant.
There were reasons for Infiniti's naming change-up, however. At the time, Infiniti said that the reason for the change was that the model names didn't make anybody think "Infiniti" and that "Q" was a largely unused number that would be possible to trademark. Now the company is explaining once more that Q is for cars and QX is for SUVs, and explaining for the first time that the Q is an homage to Infiniti's first car, the Q45.
Honestly, we think this new appeal to heritage is an after the fact attempt to give some more credibility to the names.