Where does “duodecennale” come from?
duodecennale (Italian) comes from Italian decennale, from Latin decennālis, from Latin decennium, from Latin decennis, from Latin annus, from Proto-Italic atnos, from Proto-Indo-European h₂et-no-, from Proto-Indo-European h₂et- — grass.
duodecennale (Italian): duodecennial
Ancestry of “duodecennale”, step by step