"The historical
origin of flags dates back to around 1000 BC, when
the Egyptians used primitive versions of flags -
some were even made out of wood or metal. Flags
were originally used for the purpose of
identification or to signal to others. Although
flags are still used for many of those reasons
today, flags have also come to be used for much
more. Flags have also been important symbols on
land as well as on sea. The military also made use
of flags to rally its troops. In military times,
capturing an enemy's flag was considered an
honorable seizure. Although the most popular use of
flags today is to identify the world's countries,
the use of national flags didn't become commonplace
until the 18th century. National flags are now used
to identify each country and their symbolism."
http://www.worldflags101.com/