For a short space of time the WTS used the phrase "Jehovah's Christian Witnesses" but then dropped the "Christian." I was told that an ex-jw group copyrighted "Jehovah's Christian Witnesses" and used it in the name of their organization and fooled many jws that looked in the phone book for the nearest KH or phone contact. That may be the same reason why the WTS put it in the KM that no KH's would have it listed on their signs, Jehovah's Christian Witnesses.
I have heard that as well from an elder who looked up another congregation in the phone book.
I usually said "one of Jehovah's witnesses" because Jehovah is a real person and grammar is important. I now fully understand saying "a Jehovah Witness" because why not? It's easier and the name is cult speak anyway.
Jehovah's witnesses and the Ba'hai Faith should get together and hang out.