Here is an excerpt from my upcoming book "Tea: a Nerd's Eye View." Victor Mair, whose work is the source for this blogpost, is Professor of Chinese at the University of Pennsylvania. I had the privilege of meeting him first through my brother-in-law, who was his classmate as they were working on their PhDs in Chinese at Harvard, and subsequently at the extraordinary exhibit of the Tarim mummies at the University of Pennsylvania (Here's a Youtube video of his talk about the mummies). Since the publication of his book with Erling Ho, "The True History of Tea," he has been in demand as a speaker at tea events throughout the US, including one at my old academic home, Cornell University, entitled "Tea High and Low: Elixir, Exploitation and Ecology Conference" (October 26 - 27, 2018) where I had the pleasure of meeting him again.
According to sinologist and linguist Victor Mair, as outlined in Appendix C of his book with Erling Ho, “The True History of Tea,” the words used for tea in the world’s languages have followed the paths taken by the leaf itself.
The genetics of the Camellia sinensis plant show that it was first cultivated in areas neighboring the Yun-Gui plateau, while it was used as a wild plant both there and in the corner joining Southwest China, Tibet, India, Bhutan, and Myanmar/Burma.
The languages spoken in the Yun-Gui area belonged to the Austro-Asiatic group, the oldest language group South Asia. These languages appear to have spread south from there along the course of the Lancang/Mekong River, where we find both wild and cultivated Camellia sinensis today.
In the Austro-Asiatic language group the word for a leaf was originally “*la.” (The asterisk indicates a reconstruction.) People speaking Mon-Khmer languages, a language group descended from Austro-Asiatic, settled among the botanic riches along the Irawaddy, Lancang/Mekong and Nu/Salween rivers. “La” became the specific term for Camellia sinsnsis when consumption of the leaf as a fermented salad or chew became an integral part of their culture, and variations on the theme of tea infusions were practiced, probably about 5000 years ago, or possibly earlier.
Sinetic-language speakers (= people who spoke some form of what was eventually become one or another variant of Chinese) came into contact with the Mon-Khmer people and their tea culture some 3000 years ago, and began the deliberate cultivation of Camellia sinensis in what is now Sichuan.
The “First Emperor” Qin Shi Huang (also called Shi Huangdi) conquered the people living and growing Camellia sinensis in Sichuan, and, by 221 BCE, brought the practice of drinking tea into Chinese culture.
Eventually, cultivation spread, to neighboring Fujian in particular where the plant may have hybridized with local wild plants to give the many different leaf forms now seen in Fujian.
In the sinetic Southern Min language of Fujian and Taiwan, “*la” was transformed via “dra”—apparently an old sinetic form—into “te.”
Outside the Southern Min-speaking areas “*la” evolved into “cha,”
Tea was brought to Korea and Japan via the northern route, so the word in those languages is “cha.”
The Portuguese were the first to bring tea to Europe and called it “cha,” the pronunciation in Guangdong—they held Macao in that province until 1999. However this pronunciation did not gain traction in the rest of Europe, because the quantities of leaf imported were so small.
It took the Dutch to bring large quantities of tea to Western Europe in the 17th century. They traded in Amoy (now called Xiamen), in Fujian, as well as in Formosa (now Taiwan) and brought the “te” pronunciation with them to Western Europe.
“Chai” sounds like a transformation of “cha.” According to Victor Mair, it is indeed a transformation of “cha,” one first created in Persian to become “chay.” People on the land routes through Central and Western Asia to the Middle East and Eastern Europe used Persian as a common language of trade at the time when tea drinking spread to these areas.
Thus “chai” was brought to India from Central Asia by the Moghuls in the 16th century, then picked up in Hindi-Urdu, and finally it came into English.