Where does “decado” come from?

decado (Latin) comes from Latin cadō, from Proto-Italic kadō, from Proto-Indo-European ḱad- — to fall.

Ancestry of “decado”, step by step

Step	Language	Word	Meaning
1	Latin	cadō	to fall, to fall out
2	Proto-Italic	kadō	fall, sink
3	Proto-Indo-European	ḱad-	to fall