(a) " 'Paper tiger' is one of a handful of Chinese idioms that have been translated directly into English through a process that linguists call 'loan-translation' or 'calquing.' Other examples include 'running dog,' 'brainwashing,' and 'losing face.'
In Mandarin Chinese, the expression zhilaohu (from zhi meaning 'paper' and laohu meaning 'tiger') goes back to the 14th century, during the early Ming dynasty. Even then, the figure of the paper tiger represented an empty threat. In the classical novel 'Water Margin 水浒传,' credited to the writer Shi Nai'an [明朝] 施耐庵, a character says, 'But when the time comes for action, what good are you? Seeing a paper tiger, you cry out in fright.'
(b) "But 'paper tiger' didn't get popularized in English until the 1964 translation of Mao Zedong's 'Little Red Book,' which asserted that 'imperialism and all reactionaries are paper tigers.' Mao had described the US as a 'paper tiger' as early as 1956, observing, 'Outwardly a tiger, it is made of paper, unable to withstand the wind and the rain.