The "T" in T-shirt stands for "tee" or "tee shirt". This connection stems from the phonetic pronunciation of the letter "T" as "tee" in English. The most widely held explanation for the name is that the "T" in T-shirt simply refers to the basic shape of the garment - a simple vertical body with horizontal arms which resembles a capital letter T. The T-shirt evolved from undergarments used in the 19th century and, in the mid-20th century, transitioned from undergarments to general-use casual clothing. T-shirts were originally worn as undershirts, but are now worn frequently as the only piece of clothing on the top half of the body, other than possibly a brassiere or, rarely, a waistcoat (vest) .