Where does “[[veřěj]], [[veřěje]]” come from?

[[veřěj]], [[veřěje]] (Old Czech) comes from Proto-Slavic verěja.

Ancestry of “[[veřěj]], [[veřěje]]”, step by step

Step	Language	Word	Meaning
1	Proto-Slavic	verěja	—

[[veřěj]], [[veřěje]] — Etymology, Origin & Word History | Etymology Explorer