Where does “очеретъ” come from?

очеретъ (Old East Slavic) comes from Proto-Slavic *o(b)čertъ — reed.

Ancestry of “очеретъ”, step by step

StepLanguageWordMeaning
1Proto-Slavic*o(b)čertъreed
Every word from Proto-Slavic *o(b)čertъ