Most likely, the word borscht comes from the name of the plant - hogweed (in Ukrainian borschivnyk), whose edible leaves were used for the preparation of several dishes. It is widely believed that "borscht" is the old Slavic name for beets: this association is not registered in ancient Slavic dictionaries but we know instead, that the soups prepared, when they contained the panace were called borscht.
Common hogweed