In my view, "arc" refers to the length of a curve ("curve" as distinctive from a straight line).
But that's already a criticism to the use of "arc" in the context of superlogarithm: the length of the piece of trajectory, (according to the difference of heights at two distinct points (x1,f(x1)) ... (x2,f(x2)) is not meant by the superlogarithm, for which another name was sought. So "arc" seems to be not a special good choice for the inverse of tetration. (in the case of a circle it is the length of the curve, proportional to the angle)
Gottfried
But that's already a criticism to the use of "arc" in the context of superlogarithm: the length of the piece of trajectory, (according to the difference of heights at two distinct points (x1,f(x1)) ... (x2,f(x2)) is not meant by the superlogarithm, for which another name was sought. So "arc" seems to be not a special good choice for the inverse of tetration. (in the case of a circle it is the length of the curve, proportional to the angle)
Gottfried
Gottfried Helms, Kassel