Why programmer remember only 'i' for loop

Question

Why?

Answer 1

i= initial value
i= initial condition
i= increment

Answer 2

This behaviour may have its origin in FORTRAN programming language, where the (first) letter of a variable determines the data type. Variables beginning with I,J,K,L,M,N are integer variables (i for integer).

Look at section 5.3 of the first FORTRAN standard from 1966:

http://web.eah-jena.de/~kleine/history/languages/ansi-x3dot9-1966-Fortran66.pdf

or page 10 of the first FORTRAN manual from 1956:

https://www.fortran.com/FortranForTheIBM704.pdf