Where does “sana” come from?

sana (Javanese) comes from Old Javanese saṅa, from Sanskrit आसन, from Sanskrit आस्ते, from Proto-Indo-Aryan Hā́stay, from Proto-Indo-Iranian Hā́stay, from Proto-Indo-European h₁ḗsti, from Proto-Indo-European h₁ēs- — to be.

Ancestry of “sana”, step by step

Step	Language	Word	Meaning
1	Old Javanese	saṅa	nine
2	Sanskrit	आसन	seat, chair; a comfortable position; sitting,...
3	Sanskrit	आस्ते	to be; to stay; to sit
4	Proto-Indo-Aryan	Hā́stay	—
5	Proto-Indo-Iranian	Hā́stay	—
6	Proto-Indo-European	h₁ḗsti	to be
7	Proto-Indo-European	h₁ēs-	to be

Every word from Proto-Indo-European h₁ēs- →Every word from Proto-Indo-European h₁ḗsti →Every word from Proto-Indo-Iranian Hā́stay →