Where does “əmpat ratus” come from?

əmpat ratus (Proto-Malayic) comes from Proto-Malayo-Polynesian əpat ʀatus, from Proto-Austronesian Səpat ʀaCus.

Ancestry of “əmpat ratus”, step by step

Step	Language	Word	Meaning
1	Proto-Malayo-Polynesian	əpat ʀatus	—
2	Proto-Austronesian	Səpat ʀaCus	—