Which came first - the Matrix entry name convention or the Programming for loop variable name convention?

Question

So, conventionally, entries in a matrix are referred to as $A_{ij}$ - $i$th row, $j$th column.

For historical reasons (least partially due to Cobol naming restrictions based on what I've read, but I could be wrong), variable names for for loops will also be i and, for nested loops, j:

for (int i = 0; i < 10; i++) {
    for (int j = 0; j < 20; j++) {
      //..
     }
 }

Is this resemblance purely coincidental, or was one "borrowed" from the other? If one was "borrowed," which one came first?