How should one refer to the practice of using letters instead of numbers for counting?
I'm referring to this:
"A, B, C, ... X, Y, Z, AA, AB, AC, AD, AE, AF, AG... ZX, ZY, ZZ, AAA, AAB..."
Microsoft Excel uses this notation for spreadsheet columns, but I'm unaware if there's a proper name for this. "Alphabetic numbering" sounds rather nebulous, but it's the closest I can think of.
In the bijective base-26 system one may use the Latin alphabet letters "A" to "Z" to represent the 26 digit values one to twenty-six.
With this choice of notation, the number sequence (starting from 1) begins A, B, C, ..., X, Y, Z, AA, AB, AC, ..., AX, AY, AZ, BA, BB, BC, ...
Each digit position represents a power of twenty-six, so for example, the numeral ABC represents the value 1\times 26^2 + 2\times 26^1 + 3\times 26^0.
"Hexavigesimal" itself seems to refer to any numbering system that uses a radix of 26, rather than one that uses strictly alphabetic characters alone. So while it wasn't quite correct, it put me on the right path.