> Defining index as the element wise offset is a precise well formed definition/name.
But it's less precise than offset and obviously introduces confusion. Whoever originated the term "0-indexed" should have just suggested we use a better word rather than keeping the inaccurate word (proven by the fact you're currently looking for a way to remove some confusion around the currently chosen word) and prefixing it with a digit, which itself is a confusing thing to do to an English word, thus adding to the confusing while subtracting none.
you can say the same for 1-indexed, because from the get to go both existed.
Also it's not less precise, as there are many different kinds of offsets too. First you have element wise and byte wise and similar offsets, then offsets are inherently relative to something, and that's not always the first element. But could be an offset from the back and I have even seen a offset from one element before the first element in some very unusual use-cases.
But it's less precise than offset and obviously introduces confusion. Whoever originated the term "0-indexed" should have just suggested we use a better word rather than keeping the inaccurate word (proven by the fact you're currently looking for a way to remove some confusion around the currently chosen word) and prefixing it with a digit, which itself is a confusing thing to do to an English word, thus adding to the confusing while subtracting none.