Where does “бо̏ле̄ст” come from?

бо̏ле̄ст (Serbo-Croatian) comes from Proto-Slavic *bolěstь.

Ancestry of “бо̏ле̄ст”, step by step

Step	Language	Word	Meaning
1	Proto-Slavic	*bolěstь	—

бо̏ле̄ст — Etymology, Origin & Word History | Etymology Explorer