During the First World War, Daniel Jones adopted the equivalent letters in response to a 1914 call to fill this gap in the IPA, and these were published in 1921; they were formally accepted by the IPA in 1928 (see ).

In 1875, if not earlier, Wilhelm Bleek created or adopted the letter for bilabial clicks. It would be used more extensively by Lucy Lloyd in 1911and added to the IPA in 1976.