Where does “старик” come from?

старик (Bulgarian) comes from Bulgarian стар, from Proto-Slavic starъ, from Proto-Balto-Slavic staʔros, from Proto-Indo-European steh₂-ro-, from Proto-Indo-European steh₂- — to stand.

Ancestry of “старик”, step by step

Step	Language	Word	Meaning
1	Bulgarian	стар	old; out of date, obsolete, outdated,...
2	Proto-Slavic	starъ	old
3	Proto-Balto-Slavic	staʔros	—
4	Proto-Indo-European	steh₂-ro-	large, big, thick; old
5	Proto-Indo-European	steh₂-	to stand

Every word from Proto-Indo-European steh₂- →Every word from Proto-Indo-European steh₂-ro- →Every word from Proto-Balto-Slavic staʔros →