Where does “Tosto” come from?

Tosto (English) comes from Italian tosto, from Latin tostus, from Proto-Italic *torstos.

Ancestry of “Tosto”, step by step

Step	Language	Word	Meaning
1	Italian	tosto	at once, immediately; swift, rapid, hurried;...
2	Latin	tostus	roasted, toasted, scorched, having been roasted;...
3	Proto-Italic	*torstos	—