Quiz: Remember the definition of mal de mer?
"Chinese geometric puzzle," 1864, said to be an arbitrary formation based on anagram, etc. First element perhaps Chin. t'an "to extend," or t'ang, commonly used in Cantonese for "Chinese." Some suggest it is the name of the inventor, "but no such person is known to Chinese scholars" [OED]. Another theory involves the Tanka people, who were involved in the opium trade, and Western sailors who discovered the puzzle from their Tanka girlfriends. Perhaps from an obscure sense of tram. The Chinese name is Ch'i ch'iao t'u "seven ingenious plan."