Spritz was born during the period of the Habsburg domination in Veneto in the 1800s, under the Kingdom of Lombardy–Venetia. The soldiers, but also the various merchants, diplomats and employees of the Habsburg Empire
in Veneto became quickly accustomed to drinking local wine in the
taverns, but they were not familiar with the wide variety of wines from
the Veneto, and the alcohol content was higher than they were accustomed
to.

The newcomers started to ask the local hosts to spray a drop of water into the wine (spritzen,
in German) to make the wines lighter; the real original spritz was composed of sparkling white wine or red wine diluted with fresh water

Between 1920's and 1930's, in Padova or Venice, Spritz was combined with local bitters (usually drunk with soda and ice). After all, Aperol was born in Padua in 1919 and Select in Venice in 1920.

Source: WIKIPEDIA