Really, the Scriptures themselves act as a conclusive "eyewitness" statement that early Christians did in fact use Jehovah's name in their writings, especially when they quoted passages from the Old Testament that contain that name.
Tota Dikwalo ka botsone di supa kwantle ga pelaelo gore Bakeresete ba bogologolo ba ne ba dirisa leina la ga Jehofa mo mekwalong ya bone, segolobogolo fa ba ne ba nopola ditemana go tswa mo Tesetamenteng e Kgologolo tse di neng di na le leina leo.