A T-shirt... The T in T-shirt is there because the T-shirt is shaped as a T as also the shirt means (this is what I have ALWAYS been told by everyone I have ever asked) so as i was saying it means...
The "T" was never meant to stand for anything - the etymology is based on the shape of a T-shirt when it's laid flat, and how the body and sleeves make a capital-T shape. The term has its origins...