The term comes from the Japanese word boke the “blur quality”. The Japanese term boke is also used in the sense of a mental haze or senility. The term bokashi is related, meaning intentional blurring or gradation.
The English spelling bokeh was popularized in 1997 in Photo Techniques magazine, when Mike Johnston, the editor at the time, commissioned three papers on the topic for the March/April 1997 issue; he altered the spelling to suggest the correct pronunciation to English speakers, saying “it is properly pronounced with bo as in bone and ke as in Kenneth, with equal stress on either syllable”.