The two examples given in support of short local variables names rely heavily on convention or prior knowledge. I don't think they're strong arguments for making short variable names.

Naming the integer counter "i" is convention learned in CS class (initially) that has become common usage. If you have nested for loops then j, k are often conventional for naming the next counter variables, though without an enclosing "i" they would look strange to most people.

Likewise, tmp draws on existing knowledge of /tmp as the location for temporary data on Unix machines.