[for moon i] I asked because I was bored

I understand why variables such as Python, c, and java are declared with a, b, n, m, x, and y. Since a or b is the first in abcde order, you can think of it as "n" for number and "m" for number and "m" for number and "n" for coordinates, so I think you can see it, but I can't find much results when I search for "for, while. What is the origin of i?