No, you're talking about Hungarian notation, the guide is talking about standardised one-letter names for certain variables.
I don't recommend one letter variables. I don't know if I've ever seen an official style guide that has.
Not that familiar with idiomatic Ruby, but using one letter variables as iterators in for loops (and some other things) is pretty idiomatic C:
int i;
for (i = 0; i < queue_size; i++)
queue[i] = get_rarest_peer(t->peer_list); [1, 2, 3].each { |e| puts e }
Object.methods.each { |m| "Method is: #{m}" } [1, 2, 3].each { |value| puts value }
Object.methods.each { |method| "Method is: #{method}" }