Definition of "twankay"

Hyson, including superior Twankay, at 3s.

1827 December, The Asiatic Journal and Monthly Miscellany‎, volume 24, page 798

The varieties of green tea are, twankay, and several kinds of hyson: the former is a coarse article.

1837, “On Dietetic Chemistry”, in Magazine of Popular Science, and Journal of the Useful Arts‎, volume 3, page 252

There is now scarcely any bohea or twankay imported (at least under those names) to what there was formerly.

1856, Leone Levi, Annals of British Legislation‎, volume 1, page 18