Hand wave = magical
When I was a kid, we'd wave our hands in a mysterious way and say abra kadabra and then poof, we'd achieve magical results. Well, we'd pretend but a hand wave means some kind of mysterious magical action that gives results not attainable by normal human means.
When you stayed up all night programming to get something difficult completed and someone asks, "How in the world did you do that?" To be falsely modest, you reply, "Oh I just did the old hand wave and poof, it appeared."