Tee/tee shirt/t-shirt named after the T shape of the body and sleeves. The word t-shirt became part of American English by the 1920s. The t-shirt evolved from undergarments used in the 19th century, through cutting the one-piece union suit underwear into separate top and bottom garments, with the top long enough to tuck under the waistband of the bottoms. With and without buttons, they were adopted by miners and stevedores during the late 19th century as a convenient covering for hot environments.
As slip-on garments without buttons, they originally became popular in the United States when they were issued by the U.S. Navy during or following the Spanish–American War of 1898. These were a crew-necked, short-sleeved, white cotton undershirt to be worn under a uniform. It became common for sailors and Marines in work parties, the early submarines, and tropical climates to remove their uniform jacket, wearing (and soiling) only the undershirt. They soon became popular as a bottom layer of clothing for workers in various industries, including agriculture.
The t-shirt was easily fitted, easily cleaned, and inexpensive, and for those reasons it became the shirt of choice for young boys. Boys’ shirts were made in various colors and patterns. By the Great Depression, the t-shirt was often the default garment to be worn when doing farm or ranch chores, as well as other times when modesty called for a torso covering but conditions called for lightweight fabrics.
A v-neck t-shirt has a v-shaped neckline, as opposed to the round neckline of the more common crew neck shirt. V-necks were introduced so that the neckline of the shirt does not stand out when an outer shirt is worn over it, thus reducing or eliminating the visible cloth above the outer shirt of a crew neck shirt.