I always though this English expression is a bit odd.
I mean, Jack Robinson is not such a short name, I could slap someone pretty hard before he could say Jack Robinson.
I mean, OK, at least it's not "Before you could say Arnold Schwarzenegger" but it could be way shorter like John Doe or something.
That's why I was felt respect for the Japanese language when I stumbled on this expression with the same meaning, but more logical, in my opinion.
Meaning: a blink of time
Literally: the time it takes to say "Ah!"
And just like that, before we can say "Ah!", this entry is done!