There are two girsa'ot as to what precedes "Tavo"
"Elokeinu v'Eilokei Avoteinu".
In old machzorim Elokeinu etc.
Was often abreviated AV"A
Where A = Aleph and V = Vav
ANA is the same with the Nun in place of the Vav - and w/o the abbreviation.
As it turns out - AV"A resembles ANA in the fonts of Old Machzorim
While I'm not certain which was the original Nusach, I'm still quite convinced this is how the confusion started
I would guess that AV"A aka Elokeinu is more likely correct because it is so frequently used in Y"K to introduce various paragraphs.