According to my surfing about Betta Splendens, it was first found by Thailand people. The people of Siam (now Thailand) originally started to collect these fish, then known as "pla kat," which means tearing or biting fish, prior to the 19th century.
In the wild, bettas spar for only a few minutes or so before one fish
backs off. Bred specifically for fighting, domesticated betta matches
can go on for much longer, with winners determined by a willingness to
continue fighting. Once one fish retreats, the match is over. Large
amounts of money are wagered during these fights, with potential losses
as great as a person's home.
Seeing the popularity of these fights, the King of Siam started
licensing and collecting these fighting fish. In 1840, he gave some of
his prized fish to a man who, in turn, gave them to Dr. Theodor Cantor, a
medical scientist. Nine years later, Dr. Cantor wrote an article
describing them under the name Macropodus Pugnax. In 1909, Mr. Tate
Regan realized that there was already a species with the name Macropodus Pugnax, and renamed the Siamese fighting fish to Betta splendens.
Source:http://en.wikipedia.org/wiki/Siamese_fighting_fish
