The sling as a weapon was already known to Neolithic peoples around the Mediterranean, but it is likely to be much older. Rome of course used it.
The Frombolatore or Fromboliere is an old war machine. The possibility of hitting the enemy from far away was a precious skill, and it was quite used in the Roman Army too.
The Frombolatore represented the power of artillery in a sling, before the invention of gunpowder (here in the West countries, at least).
Throwing heavy stones against the enemy, was not an easy job, and quite an important one.
The Balearic slingers - which were considered the best slingers of the ancient times - were trained already when kids to hit the target with maximum precision.
In the Venice Carnival the supposed Frombolatore skills were used to have fun, of course, but I would be little surprised if these Mattaccini - in throwing their perfumed eggs - were very rarely hitting their targets and only making big messes ...