A Bento in general is a Japanese box that is usually compartmentalized and used to serve lunch (the word "bento" simply means lunch in Japanese - though you would say obento if you were a woman and bento if you were a man). These boxes usually are heavily lacquered insides and sometimes outsides. Since food needs to go into them I guess lacquer formed a kind of early version of a non-stick surface. The phrase bento bako literally means "lunch box". Nowadays - most of these are plastic and have a "lacquered" surface painted on, but traditionally these boxes would have been made of wood and have been dipped or painted with lacquer.