אנא השם...אנא בשם כפר...
“I beg You Hashem…I beg You, with The Name forgive….”

QUESTION: Why does the Kohen Gadol first say “Hashem” and later says “Besheim”?

ANSWER: Hashem’s Ineffable Four Letter Name (The Tetragramaton) is spelled, “yud, hei, vav, hei.” Ordinarily it is pronounced “A-donoy” and not as it is written. In his confessions on Yom Kippur the Kohen Gadol would pronounce the Ineffable Four Letter Name as it is spelled.

The first time he mentions it he is addressing Him directly, and thus he says “Ana Hashem” — “Please G‑d.” After addressing Him he appeals, “Ana Besheim” — “Please use the Name, which represents absolute mercy, to grant forgiveness on this Yom Kippur day.”

(ירושלמי הובא ביומא ל"ה ע"ב תוד"ה אנא, ועי' שו"ע אדמוה"ז תרכ"א:י"א)

When the Kohanim would hear the Kohen Gadol pronounce this Name, they would respond after him; “Baruch sheim kevod malchuto le’olam va’ed” — “Blessed be the Name of the glory of His kingdom forever and ever.” Perhaps this is another reason why we say this passage on Yom Kippur loudly, to emphasize that it was through The Name that G‑d granted forgiveness to Klal Yisrael.

(הרב יוסף דוב הלוי ז"ל סאלוווייטשיק – מבאסטאן)