Footnote
As to the occurrence of the name Jehovah here, the footnote b on Isaiah 6:1 as given in Volume 4 of the New World Translation of the Hebrew Scriptures, edition of 1958, says: “‘Jehovah,’ Syriac and about 100 Hebrew manuscripts; ‘the dignity of Jehovah,’ Targum, ‘the Lord,’ LXX; Doʹmi·nus, Vulgate A·do·nayʹ, Masoretic and Dead Sea Scroll of Isaiah. This is one of the 134 passages in which the Jewish Sopherim changed the primitive Hebrew text to read A·do·nayʹ instead of Yeho·wahʹ.”
See also the footnote on Isaiah 6:1 as given in Dr. Adam Clarke’s Commentary, Volume 4.