Corvette is shortened to 'Vette, Mustang is shortened to 'Stang, why?

[blanderswake]

why is Tacoma shortened to Taco? Shouldn't it be 'Coma?
I know why it's done on the 'Vette and the 'Stang. I do it myself all the time. It was just awkward wording the question the right way.

And yes, I do have WAY too much time on my hands.