The word, tattoo originates from the Tahitian word tattau, which means "to mark" It has also been speculated that tattoos were originally an accident. This is because the Samoan word, "tatau" literally means "open wound." Scientists and Historians around the world believe that thousands of years ago, someone had a scratch or other sort of small wound.
This person more than likely wiped the blood from the wound off with their hand, which was covered with ash and soot from a fire. Of course, once the wound healed - they found a permanent mark was left behind. By inserting colored materials into open wounds have also been speculated to been used to honor a worrier for his heroic deeds or acts of valor and was permanently visible beneath the skin's surface.
However, some scientists believe that the earliest known evidence of tattooing dates back to markings found on the skin of the Iceman, a mummified human body that dates as far back as 3300 B.C.
More widely recognized are tattoos found on Egyptian and Nubian mummies dating from about 2000 B.C. Classical authors mention the use of tattoos in connection with Greeks, ancient Germans, Gauls, Thracians and ancient Britons.
Tattooing was rediscovered by Europeans when they came into contact with Polynesians and American Indians through their explorations. Because tattoos were considered so exotic in European and U.S. societies, tattooed Indians and Polynesians amazed crowds at circuses and fairs during the 18th and 19th centuries. The Ainu, the indigenous people of Japan, wore facial tattoos, as do some Maori of New Zealand to this day.
The practice of tattooing has different meanings to various cultures. Decoration was the most common motive for tattooing and that still holds true today.
Historically, tattoos consisted of symbols that represented religious beliefs, forms of decoration for bravery (much like a medal,) or even protection. They were also used as a form of punishment to mark convicts and criminals.
military forces like The US Army, The British Navy, etc - in honor of their country, their family, or branch they belong to.