pneumonoultramicroscopicsilicovolcanoconiosis (n.)youdaoicibaDictYouDict[pneumonoultramicroscopicsilicovolcanoconiosis 词源字典]
1962, "A facetious word alleged to mean 'a lung disease caused by the inhalation of very fine silica dust' but occurring chiefly as an instance of a very long word" [OED]. Said in an early reference to have been invented by seventh grade students in Norfolk, Virginia.[pneumonoultramicroscopicsilicovolcanoconiosis etymology, pneumonoultramicroscopicsilicovolcanoconiosis origin, 英语词源]