Where does “decenniad” come from?

decenniad (English) comes 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.

decenniad (English): A decennium: a period of ten years

Definitions

A decennium: a period of ten years

Ancestry of “decenniad”, step by step

Step	Language	Word	Meaning
1	Latin	decennium	decennium; decade
2	Latin	decennis	decennial, of ten years
3	Latin	annus	year; time; season
4	Proto-Italic	atnos	year
5	Proto-Indo-European	h₂et-no-	—
6	Proto-Indo-European	h₂et-	grass

Every word from Proto-Indo-European h₂et- →Every word from Proto-Indo-European h₂et-no- →Every word from Proto-Italic atnos →