Where does “Lao” come from?

Lao (Tagalog) comes from English lao, from Lao ລາວ — he, she, him, her.

Ancestry of “Lao”, step by step

Step	Language	Word	Meaning
1	English	lao	A Tai ethnic group native to Southeast Asia
2	Lao	ລາວ	he, she, him, her