Where does “ultimissimo” come from?

ultimissimo (Italian) comes from Italian ultimo, from Latin ultimus, from Proto-Italic *oltm̥mos — last.

Ancestry of “ultimissimo”, step by step

StepLanguageWordMeaning
1Italianultimolast; recent, current; pertaining to last month
2Latinultimuslast, final; furthest, farthest
3Proto-Italic*oltm̥moslast
Every word from Proto-Italic *oltm̥mos →Every word from Latin ultimus →Every word from Italian ultimo →