All are referring to the same tea.
Oolong is generally used in the western hemisphere and wulong or wu-long is generally used in China and
Chinese speaking community of the world.
The name evolved from Wu Liang in the south Fujian dialect.
The name is tied in to the legend of its origins.
The tale begins with the first cultivator of the tea Wu Liang.
He had harvested several pounds of tea growing wild in the mountains one day.
As it so happened he also caught a river deer the same day and was busy when he got home that day, prepping his hunt.
As a consequence he had neglected to dry the tea leaves.
The next day, when he set out to care for the tea leaves he found that they had fermented from being stored in the basket overnight.
He immediately roasted the tea in the wok.
He proceeded to brew himself a pot and found to his surprise that the brew tasted mellow with no bitter or astringent taste.
He proceeded to share the tea and his ‘accidental recipe’ with the village. Everyone in the village liked the fermented tea and they named it Wu Liang Tea.
However, according to the Tribute Tea theory, the oolong tea is a direct descendant of the Dragon Phoenix Tea Cake Tribute tea.
The tribute tea was replaced by the oolong tea as loose leaved teas came into favor.
It was called the Black dragon tea because it was dark, long and curly.
Historically, the evidence of oolong tea is traced back to the Qing dynasty in the poems of Wuyi Tea Song – Wuyi Chage and the Tea Tales – Chashuo.