Which is why I don't like it. It's awkward to say and awkward to use.
It is a Japanese word (Romaji: boke; pronounced as two syllables, soft vowels in both), the literal translation being "blur". Us westerners like to append the h so that other ignorant roundeyes don't pronounce it as rhyming with broke.
At best it gets pronounced bokay or bokuh, because in English an "eh" on the end of of a word is never pronounced like the "e" in "end".
So: to describe a property of lenses, Mike Johnston introduced a word that no one understood the meaning of, and which no English speaker would know how to pronounce properly, and might not be able to even after having it explained. Further, the property is judged subjectively, ensuring that there would be misuse whenever his intended exact meaning of the word is not understood.
Johnston's attempt to bring clarity to a concept by introducing a standard word for it instead created a muddled linguistic and conceptual mess.