Carnival has always been also a way of flirting, getting sexes together.
One way of courting (making passes at) women in the ancient Carnival times (XIII century!) started to be the unusual throwing of eggs filled up with rose water. And it quickly became a trend.
But the “Giuoco degli ovi”, as it was called, was prohibited on May 2, 1268, so it couldn’t be played in the San Marco Square anymore.
“Ovorum ludus
circa ecclesiam S Marci est prohibitus”
“Eggs game is prohibited around S.Marco Church”
But in 1548 the habit of throwing perfumed eggs became in fashion again.
At the time hundreds of street vendors were selling perfumed eggs to be thrown against friends or spectators or young women in love and were selling different kinds of perfumed eggs, good or bad smelling, maybe.
And young masked men were going around town, showing their appreciation for the ladies they liked most, throwing these perfumed eggs in front of their houses and windows, or even some ugly lady, just for a tease.
As it happens the joke would become too wild, sometimes, so eggs also went towards the spectators, the ladies' husbands, and finally to the ladies themselves …
This activity became so popular and usual that many houses started getting organized, putting nets in front of the windows.
These "eggs throwing masks" were also known as Mattaccino or Frombolatore (the name comes from the ”frombola”, the sling).