You may notice that some drivers give an open palm gesture to each other, thrusting their hand forward like in high-five motion and uttering grumbling sounds as “Naaa! Malaka!”. It’s a kind of an offensive curse of Byzantine, or French, or Venetian origin when chained prisoners were paraded through the streets and abused by having handfuls of filth from the gutter picked up by onlookers and thrust into their faces. But seriously now, they offer some excitement in a dull hot Athens day.
source: https://www.bestofathens.gr/article/moutza