{ Congou (?), Congo (?) }, n. [Chin. kung-foo labor.] Black tea, of higher grade (finer leaf and less dusty) than the present bohea. Also called English breakfast tea. See Tea.
[1913 Webster +PJC]

Of black teas, the great mass is called Congou, or the “well worked”, a name which took the place of the Bohea of 150 years ago, and is now itself giving way to the term “English breakfast tea.” S. W. Williams.
[1913 Webster]